1. 骑行锻炼的效率评估：能量消耗与健康收益
1.1 骑行的能量代谢特征与心肺功能提升
骑行作为一种受欢迎的有氧运动形式，其能量代谢特征和对心肺功能的提升作用是评估其锻炼效率的关键。研究表明，骑行期间的能量消耗与运动强度密切相关。通勤骑行在个体自我选择的强度下，平均代谢当量（MET）可达6.8（标准差1.9），能量消耗约为每小时540千卡，每周总能量消耗可达1539千卡，这符合美国疾病控制与预防中心（CDC）和美国运动医学会（ACSM）关于健康改善的建议，并有助于心肺功能的提升 1。
在不同强度下，骑行的能量消耗效率有所差异。研究指出，脂肪氧化率在低至中等强度运动中增加，在强度较高时则下降。在训练有素的个体中，最大脂肪氧化率在最大摄氧量（VO₂max）的59%至64%强度下达到，而在普通人群中则在47%至52%的VO₂max强度下达到 2。这意味着中等强度的骑行更利于脂肪作为能量来源。
骑行对心肺功能的提升主要体现在最大摄氧量（VO₂max）的提高。VO₂max是衡量心肺健康的重要指标，表示身体在最大运动强度下摄取、运输和利用氧气的最高能力 3。虽然跑步通常能达到更高的VO₂max值，但骑行同样能有效提升这一指标 4。例如，高强度间歇训练（HIIT）在短时间内（2-4周内进行6-8次训练）可使训练有素的运动员的运动表现提升2-4% 5，这部分归因于心肺功能的改善。此外，研究发现规律性的非运动性体力活动与心率恢复能力呈正相关，而心肺适应性（VO₂max）则与心率变异性（HRV）相关 6。这表明骑行不仅通过强度训练提升心肺功能，其作为日常通勤或休闲活动也能带来累积的健康益处。
与传统有氧运动如跑步和游泳相比，骑行的能量消耗模式略有不同。例如，有研究表明，相同强度下跑步的脂肪氧化率高于骑行 2。然而，不同运动模式间的生理差异，例如VO₂max和乳酸阈值，会受到运动模式特异性的影响 4。尽管如此，无论是骑行、跑步还是游泳，耐力运动均能引起身体的适应性变化，从而提高能量利用效率和心肺耐力 37。对于儿童而言，骑行等运动的能量消耗比成人更高，即使调整了去脂体重（FFM）和年龄差异后，儿童每日总能量消耗和睡眠时能量消耗仍显著高于成人，这可能与儿童体内器官的比例更高有关 8。
长期骑行训练可导致心血管系统发生适应性改变，例如改善内皮功能，这对于预防和管理高血压具有重要意义 9。总而言之，骑行是一种高效的锻炼方式，尤其在提升心肺功能和能量代谢方面具有显著效果，且其强度可根据个人需求调整，以实现不同的健康目标。
1.2 电助力骑行（e-bike）的特殊效率与人群适应性
电助力骑行（e-bike），作为一种新兴的出行与锻炼方式，正在改变人们对传统自行车运动的认知。与传统自行车相比，电助力自行车通过电力辅助降低了骑行所需的体力，从而拓宽了其适用人群和使用场景，尤其对于久坐人群、体力活动不足者及中老年群体而言，具有独特的健康效益 10。
电助力骑行能够显著提升体力活动水平。一项系统综述和荟萃分析指出，电助力骑行虽然相较于传统骑行，能量消耗（EE）、心率（HR）、摄氧量（VO₂）和代谢当量（METs）等生理响应较低，但仍能产生足以带来健康益处的生理响应 11。具体而言，电助力骑行的心率响应平均比传统骑行低约11.41次/分钟，摄氧量也相对较低 11。然而，与步行相比，电助力骑行仍能带来更高的心率和摄氧量响应，表明其提供了比步行更强的运动强度 11。例如，当电助力自行车配备30公斤货物时，其运动强度仍能达到4.9 METs，显著高于驾驶汽车时的1.4 METs 12。
对于不常运动或体力较弱的人群，电助力骑行有效降低了运动门槛，从而鼓励他们参与体力活动。有研究表明，电助力自行车使用者每周骑行时间更长，总骑行距离也更远 13。一项针对日常通勤者的研究发现，电助力自行车骑行时的平均心率为109次/分钟，而传统自行车骑行时的平均心率为118次/分钟 13。这表明电助力骑行能够提供中等强度的体力活动，达到甚至超过世界卫生组织推荐的每周150分钟中等强度体力活动标准 14。
电助力骑行对心肺功能的改善作用也得到了证实。对于久坐不动的人群，电助力骑行被证实可以有效提高心肺健康水平 14。一项针对2型糖尿病患者的随机对照试验显示，为期12周的电助力骑行干预能够改善血糖控制、提高健康相关生活质量和心肺适能，并增加中高强度体力活动的时间 15。即使在崎岖路段，电助力骑行也能使大部分骑行时间处于中高强度体力活动（MVPA）范围，尽管MVPA时间略少于传统自行车，但其降低了行程时长和运动强度，使得更多人能够完成骑行 16。
此外，电助力自行车还克服了传统自行车在载重方面的局限性。例如，电动货运自行车（e-cargo bike）能够承载更多货物（如30公斤），这使其成为替代汽车出行的良好选择，尤其是在需要携带杂货或儿童的场景下，既增加了体力活动，又减少了温室气体排放 1217。总的来说，电助力骑行以其独特的电力辅助机制，有效提升了运动的可及性和依从性，特别适用于那些因体力限制或便利性需求而较少参与传统运动的人群，从而在更广泛的人群中促进了心肺功能改善和健康水平提升。
1.3 骑行与其他运动的综合效率对比
在评估骑行作为一种锻炼方式的综合效率时，有必要将其与跑步、游泳等其他常见运动形式进行多维度对比，包括肌肉激活范围、关节负荷和运动依从性，以全面理解其在整体健康促进中的优势与局限性。
从肌肉激活范围来看，骑行主要侧重于下肢肌肉群的锻炼。股四头肌（股内侧肌、股直肌、股外侧肌）和腘绳肌（股二头肌、半腱肌、半膜肌）是踏板过程中主要的发力肌肉，同时小腿肌肉（腓肠肌、比目鱼肌）和臀大肌也参与其中。与跑步相比，骑行对神经系统功能的损害程度更小，例如，在长时间（3小时）高强度运动后，骑行引起的神经系统功能损伤（特别是脊髓层面）小于跑步，而跑步引起的肌肉收缩功能损伤则大于骑行 18。这意味着骑行可能在肌肉疲劳机制上与跑步有所不同，在相同运动负荷下，骑行对中枢神经系统的疲劳影响较小，有助于延长运动持续时间。然而，跑步作为全身性运动，能更广泛地激活核心肌群和上肢肌肉，而骑行则需要额外的核心力量训练来弥补这一不足。在重复冲刺训练中，跑步会引起中枢性疲劳，而骑行则不会，尽管两者都会导致外周疲劳 19。这提示了不同运动模式在神经肌肉疲劳机制上的差异。
在关节负荷方面，骑行相较于跑步具有显著优势，尤其是在保护关节方面。跑步是一种高冲击性运动，会对膝关节、踝关节和髋关节造成反复的地面冲击力，长期下来可能增加关节损伤的风险。相比之下，骑行是一种非负重运动，关节受到的冲击力小得多，因此对于关节炎患者、肥胖人群或从损伤中恢复的个体而言，骑行是更为温和的选择。一项研究指出，在80°坐管角（更陡峭的骑行姿势）下，股直肌的激活在曲柄周期早期增加，这可能有助于在蹬踏过程中更有效地稳定骨盆，从而可能减少对脊柱和下肢关节的非必要负荷 20。
在运动依从性方面，骑行展现出较高的潜力。电助力骑行的出现，极大地降低了骑行的门槛，使其更适合于体力较弱、不常运动或有特定健康需求的人群。这种辅助方式能够让更多人参与到体力活动中来，从而提高运动的持续性和依从性。研究表明，无论是在改善体脂率方面，还是在减少脂肪量方面，以骑行为主要形式的间歇训练（包括高强度间歇训练HIIT和冲刺间歇训练SIT）都显示出优于中等强度持续训练（MICT）的效果，并且这种益处在超重/肥胖个体和长期干预（≥12周）中更为显著 21。这意味着骑行，特别是其间歇训练形式，在减脂和改善身体成分方面具有高效性，有助于提高个体坚持运动的动力。此外，骑行作为一种交通工具，其通勤功能也增加了运动融入日常生活的可能性，从而提升了依从性。
然而，骑行也存在一定的局限性。例如，长时间或不当姿势的骑行可能导致会阴部压迫、脊柱不适（尤其在公路车骑行中，躯干前倾姿势可能增加腰椎压力）以及其他与骑行相关的特定风险。这些风险需要在骑行姿态调整、器材选择和适当休息等方面进行规避。
综合来看，骑行在心肺功能提升、能量消耗效率（尤其在减脂方面）和关节保护方面表现出色，其高依从性潜力也使其成为一种可持续的锻炼方式。尽管在肌肉激活全面性上略逊于全身性运动，但通过结合其他形式的锻炼或特定的力量训练，可以有效弥补这一不足。因此，骑行是一种高效且多益的锻炼选择，尤其适合不同健康状况和运动偏好的个体。
2. 骑行对脊柱健康的影响：生物力学机制与临床证据
2.1 骑行姿势的脊柱生物力学特征
骑行姿势对脊柱的生物力学特性及其长期适应性改变具有显著影响。理解骑行时脊柱（特别是腰椎）的曲度、骨盆倾斜以及躯干负荷的动态变化，对于评估骑行对脊柱健康的影响至关重要。
在骑行过程中，典型的姿势会使躯干前倾，这导致腰椎曲度发生明显变化。通常，在站立位时腰椎表现为生理性前凸，但在骑行时，为了实现更低的空气阻力或适应车把位置，骑行者往往会减少腰椎前凸，甚至出现腰椎后凸（即腰椎变平或向后弯曲）222324。多项研究，包括使用3D扫描和肌电分析的方法，证实了这一现象。例如，一项研究指出，与站立姿势相比，骑行时腰椎从前凸变为后凸（即腰椎屈曲）25。这种变化并非固定不变，而是随着踏板冲程的循环动态调整25。车把的高度和与车座的距离是影响腰椎曲度变化的关键因素。车把位置越低或离车座越远，骑行者为达到空气动力学姿态，其骨盆倾斜度越大，腰椎后凸程度也越显著22。
骨盆倾斜在骑行姿势中扮演着核心角色。为了配合躯干前倾和减小风阻，骑行者倾向于使骨盆向前倾斜，甚至接近水平位24。这种骨盆的姿态调整直接影响腰椎的排列。当骨盆倾斜时，腰椎的生理前凸会减小，甚至可能变为后凸24。研究发现，专业和休闲骑行者在骑行时会表现出更大的骨盆倾斜，尤其是在车把位置较低的情况下22。骨盆的这种动态变化，尤其是其在踏板冲程中的运动，也会影响脊柱和核心肌肉的激活模式。
躯干负荷在骑行时也呈现出独特的生物力学特征。在骑行过程中，部分体重会通过手部和上肢传递到车把上，从而减轻脊柱的垂直负荷。然而，随着骑行强度增加，躯干对核心肌群的稳定需求也随之增加2627。特别是当功率输出较高时（例如超过500瓦），躯干和上肢肌肉的活动水平会显著提升，以维持身体姿态和辅助力量传递26。核心肌肉（如腹直肌、背阔肌等）在骑行中的激活对于脊柱稳定至关重要。研究显示，随着骑行强度的增加，核心肌肉的激活水平普遍升高，其中腹直肌在多数强度下表现出最高的激活度27。这种核心肌群的参与有助于在躯干前倾姿势下为脊柱提供支撑，但如果核心力量不足或长时间保持不当姿势，仍可能导致脊柱承受过大压力。
长期骑行训练还会导致脊柱形态的适应性改变。研究表明，与非骑行者相比，长期骑行者可能出现站立位时胸椎后凸增加的趋势（即驼背）2228。一项针对休闲骑行者的案例对照研究发现，骑行组的脊柱倾斜度显著大于对照组（非骑行运动员），且腰椎前凸显著减少23。然而，胸椎后凸的增加并不一定直接与骑行姿势相关，也可能与其他因素有关28。有研究提示，尽管骑行时胸椎处于较低的屈曲角度，但长期骑行可能会导致站立姿势下的胸椎过度后凸28。这种适应性改变可能是在长期保持前倾姿势下，身体为维持平衡和视线方向而产生的代偿。
值得注意的是，骑行姿势对脊柱的影响是多因素的。车把类型、车把与车座的相对位置、骑行者个体解剖特征（如躯干长度、柔韧性）以及骑行强度都会影响脊柱的生物力学表现222729。例如，当采用气动把位骑行时，尽管提高了空气动力学效率，但也可能增加呼吸系统的机械负荷和通气效率下降，这可能进一步影响躯干姿态和脊柱负荷30。因此，科学的自行车设置（bike fitting）和核心肌群的强化训练，对于优化骑行姿势、降低脊柱风险至关重要。
2.2 骑行与低背痛（LBP）的关联性研究
低背痛（LBP）是全球范围内普遍存在的健康问题，而骑行作为一项流行的运动，其与LBP的关联性一直是研究关注的焦点。近年来，随着骑行运动的普及，关于骑行与慢性/复发性LBP的随机对照试验（RCT）和队列研究不断增多，为我们理解二者关系提供了更多证据。
骑行与LBP的普遍性与相关性
多项研究表明，骑行者中LBP的发生率较高。一项针对竞技和休闲公路自行车手的回顾性研究发现，高达70%的竞技骑行者和67%的休闲骑行者在骑行过程中出现疼痛，其中LBP是常见的疼痛部位之一 31。另一项针对俱乐部级别公路自行车手的调查也指出，膝关节和腰椎区域是骑行相关损伤最常见的部位 32。尽管这些研究揭示了骑行者LBP的普遍性，但值得注意的是，许多骑行者在报告疼痛的同时也报告了舒适感，这提示疼痛并非总是与运动表现或依从性完全负相关 31。
然而，骑行并非总是LBP的“元凶”，有时甚至被视为缓解LBP的潜在手段。例如，一项人口学纵向研究发现，步行或骑自行车通勤可以降低LBP的风险，特别是对于非腹部肥胖和未暴露于体力劳动风险因素的个体，效果更为显著 33。此外，有研究显示，自行车耐力项目对伴有慢性LBP的老年人是安全有效的，能改善其功能状态和幸福感 34。一项比较普拉提运动与固定自行车训练对慢性非特异性LBP患者影响的RCT发现，两种干预均能有效减轻疼痛和残疾，且在6个月随访期内无显著差异，这表明固定自行车训练作为一种全身性锻炼，对LBP患者具有积极作用 35。这些研究提示，在特定条件下，骑行可能对LBP具有预防或改善作用。
影响LBP的骑行相关因素
疼痛程度和功能障碍评分与骑行时长、车型和车把高度等因素存在一定关联。
- 骑行姿势与生物力学： 骑行时躯干前屈的姿势被认为是导致LBP的重要生物力学因素。当骑行者躯干前倾时，腰椎负荷会增加，导致椎间盘压力增大。车把的高度和与车座的距离会显著影响骑行姿势。较低的车把或更远的握把距离会促使骑行者将躯干放得更平，增加腰椎的屈曲度，从而可能增加椎间盘的压力。这种过度的腰椎屈曲，尤其是在长时间骑行中，可能导致椎间盘纤维环的应力集中和髓核移位，从而诱发或加重LBP。
- 车型： 不同类型的自行车，如公路车、山地车或通勤车，其车架几何和骑行姿势的设计差异，也会对脊柱负荷产生影响。公路车通常要求更激进的前倾姿势以追求空气动力学效率，这可能增加腰椎的压力；而山地车或城市通勤车通常提供更直立的骑行姿势，可能对脊柱更友好。
- 骑行时长和强度： 长时间、高强度的骑行可能使脊柱长时间处于不利姿势，增加肌肉疲劳和结构应力，从而增加LBP的风险。例如，一项对慢性LBP患者进行体力测试的研究发现，尽管自行车测试对于评估运动能力是可靠且可行的，但在解释结果时需考虑患者间的显著变异性 36。这表明个体对骑行负荷的耐受性差异很大。
- 核心肌群强度与控制： 核心肌群是维持脊柱稳定性的关键。如果骑行者核心肌群力量不足或控制能力不佳，将难以在长时间骑行中维持脊柱的正确对线，从而增加LBP的风险。一项RCT比较了特定躯干练习和普通练习（包括坐姿骑行）对慢性LBP患者的影响，发现两者都能改善疼痛，但特定躯干练习在减轻残疾方面效果更佳，这提示核心力量训练对LBP的重要性 37。另一项研究则直接指出，腰盆核心稳定训练（LPST）通过改善疼痛阈值和降低疼痛强度，对慢性非特异性LBP患者具有治疗作用，优于被动自动骑行干预和对照干预 38。这进一步强调了核心稳定训练在预防和管理骑行相关LBP中的关键作用。
现有证据的局限性
尽管现有研究为骑行与LBP的关联提供了宝贵见解，但仍存在一些局限性。许多研究是观察性的，难以建立明确的因果关系。样本量、研究设计（如RCT数量有限）以及对混杂因素（如既往LBP史、个体差异、自行车设置细节）的控制程度，都会影响研究结果的普适性。此外，关于骑行导致椎间盘压力具体变化的直接证据（如体内测量数据）相对较少，多数是基于生物力学模型或间接推断。未来研究需更多关注精确的生物力学测量、长期随访以及针对不同骑行人群的干预研究，以更全面地阐明骑行对脊柱健康的影响。
尽管如此，目前的证据表明，合理的骑行姿势、适当的自行车设置、以及核心肌群的强化训练，对于降低骑行者LBP的风险至关重要。
2.3 特殊人群（如脊髓损伤患者）的骑行干预效果
对于脊髓损伤（Spinal Cord Injury, SCI）患者而言，由于运动功能受限，他们面临着肌肉萎缩、骨密度下降（特别是损伤平面以下的下肢骨骼）、心血管功能障碍以及高骨折风险等严峻挑战 3940。在神经康复领域，功能性电刺激骑行（Functional Electrical Stimulation Cycling, FES-cycling）作为一种新兴的康复手段，正被广泛研究和应用，以帮助这些特殊人群改善生理功能、提升生活质量 4142。FES-cycling通过外部电刺激激活瘫痪肌肉，使其产生有节律的收缩，从而驱动患者完成骑行运动。
FES-cycling 对脊柱稳定性与骨密度的作用
脊髓损伤后，由于肌肉失用，患者的下肢骨骼会迅速且显著地流失骨矿物质，导致骨密度（Bone Mineral Density, BMD）急剧下降，进而大大增加骨折的风险 3943。FES-cycling 被认为能够通过机械负荷刺激骨骼，部分逆转这种骨质流失。多项研究证实了 FES-cycling 在改善骨密度方面的积极作用：
- 局部骨密度提升： 一项针对慢性SCI患者的长期研究发现，经过12个月大容量FES-cycling训练后，患者的股骨远端骨骺（distal femoral epiphysis）的骨小梁和总骨密度显著增加了14.4%和7.0%，总横截面积也增加了1.2% 39。这意味着在主动负荷的部位，FES-cycling能够有效促进骨形成。另一项研究也指出，六个月的FES-cycling训练能显著增加股骨远端和胫骨近端的BMD 40。
- 对骨流失的减缓作用： 早期干预尤为重要。研究表明，在SCI早期阶段（损伤后26-52天），FES-cycling可以部分减缓股骨远端骨密度的下降速度，但这种效果在停止FES-cycling后会逐渐消失 44。这提示了持续性FES-cycling干预的必要性。
- 不同方案的效果： 针对儿童SCI患者的研究发现，FES-cycling组的髋部、股骨远端和胫骨近端BMD均有显著提升，而单纯被动骑行组仅在髋部有提升，非骑行电刺激组则没有显著变化，甚至在胫骨近端出现骨量丢失 45。此外，高转速（50 RPM）FES-cycling相较于低转速（20 RPM）FES-cycling，在骨形成指标（骨特异性碱性磷酸酶）和骨吸收指标（N-端肽）方面表现出不同的趋势，低转速骑行可能更有利于改善骨骼健康，因为它能产生更大的扭矩，从而提供更强的机械刺激 46。
尽管FES-cycling在提升骨密度方面显示出潜力，但其效果通常是部位特异性的，主要发生在受到主动机械负荷的骨骼区域 39。对于脊柱稳定性，FES-cycling通过增强躯干和下肢核心肌肉的力量和协调性，有助于改善坐姿平衡和整体躯干控制，间接为脊柱提供更好的支持。
FES-cycling 在神经重塑与肌肉再负荷中的独特价值
FES-cycling 不仅仅是一种肌肉训练方式，它更深远的价值体现在对神经系统的重塑（neuroplasticity）和肌肉再负荷的促进上 47。
- 诱导神经可塑性： FES-cycling 能够提供丰富的传入刺激，激活脊髓运动中枢，从而促进神经通路的可塑性变化。有研究指出，FES-cycling可以增强脊髓损伤患者下肢脊髓感觉运动兴奋性，这对于功能恢复至关重要 48。在运动过程中，通过生物反馈鼓励患者主动尝试发力，可以进一步加速神经重塑过程 47。此外，结合手臂和腿部同时骑行（A&L cycling）比单独的肢体骑行更能增强脊髓反射的短期可塑性，提示多肢体协同运动对神经网络激活的放大效应 49。
- 改善肌肉萎缩： 脊髓损伤患者的瘫痪肢体肌肉会发生严重的萎缩。FES-cycling 通过强制肌肉收缩，能够有效逆转肌肉萎缩。例如，有研究显示，经过12个月的FES-cycling训练，大腿肌肉横截面积显著增加了35.5% 39。肌肉量的增加不仅改善了外观，也为骨骼提供了更好的保护。
- 功能性恢复： FES-cycling 不仅关注肌肉和骨骼的生理变化，更重要的是其在功能性恢复方面的作用。通过模拟正常的骑行模式，患者可以在安全受控的环境中进行重复性的运动训练，这有助于恢复运动模式和步态功能。对于卒中患者，FES-augmented active cycling training被证明在改善骑行和步行能力方面有效 50。对于脊髓损伤患者，这种训练可以提高下肢力量、改善心肺功能，并对膀胱控制等功能也有潜在的积极影响 41。
最新研究趋势与挑战
近年来的研究更加关注 FES-cycling 的个性化处方和优化刺激模式。例如，对比不同刺激模式对氧耗和刺激成本的影响，以期找到最优化的刺激参数，从而提高 FES-cycling 的能量效率和临床效果 51。同时，研究人员也在探索 FES-cycling 结合其他康复技术（如脊髓刺激 SCS）来进一步增强神经可塑性和功能恢复 47。
然而，FES-cycling 的普及和应用仍面临挑战，包括设备成本、操作复杂性以及长期依从性等问题。未来研究需要更大规模、更长期的临床试验来进一步验证 FES-cycling 的长期疗效，并优化其在不同SCI患者群体的应用方案，从而使其更好地服务于神经康复。
3. 骑行对男性睾丸健康的潜在风险：压迫、温度与氧化应激
骑行作为一项广受欢迎的运动，其对男性生殖健康的影响一直是医学界和骑行爱好者关注的焦点。尽管骑行具有显著的心血管健康益处，但长时间或高频率的骑行，特别是由于其独特的姿势和装备要求，可能对男性睾丸健康构成潜在风险。这些风险主要集中在三个方面：会阴部持续压迫、阴囊局部温度升高以及由此引发的氧化应激反应。本节将深入探讨这些潜在风险的生物学机制和临床证据，评估其对精子质量、勃起功能及睾丸整体健康的影响，并审视现有研究的证据强度与局限性。
3.1 骑行中会阴部压迫的解剖学风险
骑行过程中，男性会阴部与自行车座的接触是不可避免的，这种接触可能导致局部神经血管结构的压迫，进而引发一系列健康问题，其中最受关注的是阴部麻木和勃起功能障碍（Erectile Dysfunction, ED）。针对长距离骑行活动（如320公里以上赛事）的队列研究，为我们深入理解车座设计、骑行姿势与会阴部神经血管受压之间的关联提供了重要证据。
会阴部压迫的解剖学机制
男性会阴部是躯干与下肢交界处的菱形区域，其中包含阴部神经（pudendal nerve）和阴部动脉（pudendal artery）等重要神经血管束。这些结构在会阴部区域相对表浅，尤其是在坐骨结节之间，容易受到外部压力的影响。当男性骑行者坐在传统自行车座上时，车座的窄鼻端通常会对会阴部施加直接压力，特别是对阴囊、阴茎和会阴（位于肛门与生殖器之间的区域）的神经和血管造成压迫。这种压迫会阻碍局部血流，导致神经缺血缺氧，从而引发麻木感，并在长时间压迫下可能损害血管内皮功能，影响勃起所需的血流灌注 5253。
车座设计与会阴部压迫的关联
车座设计是影响会阴部压迫程度的关键因素。
- 有无镂空（Cutout）设计： 传统观念认为，带有中央镂空或凹槽设计的车座可以减轻对会阴部的压力。然而，研究结果并不完全一致。一项针对长距离骑行者的前瞻性队列研究（骑行距离至少320公里）发现，使用“有镂空”车座的骑行者如果经历麻木感，反而与更高的ED风险相关（风险比RR 6.0），而在没有麻木感的骑行者中，镂空车座则与较低的ED风险相关（RR 0.3）54。这表明镂空车座的效果可能因人而异，对于已经出现麻木症状的骑行者，镂空车座可能导致压力重新分布到更小的接触区域，反而加重局部压迫。另有研究指出，有镂空的车座会使会阴部特定区域的压力集中，尤其是对于女性，镂空车座可能导致感知稳定性下降和前部座压降低 5556。这提示我们在选择镂空车座时需要个体化评估。
- 车座宽度和填充： 研究发现，车座的宽度而非填充量是保护阴茎血流灌注的最重要因素 53。宽型车座能够更好地支撑坐骨结节，从而将身体重量分散到骨盆区域，而不是集中在会阴部软组织上，有效减少对阴部神经血管的压迫 53。一项研究比较了四种不同车座设计对阴茎透皮氧分压（PtcO2）的影响，结果显示，宽且无座鼻的女性专用车座对阴茎供血的影响最小（PtcO2下降20.3%），而窄且填充厚的车座则导致PtcO2大幅下降（82.4%）53。
- 车座鼻部宽度： 进一步的研究强调，车座鼻部的宽度及其有无镂空设计，对女性骑行者的座压分布和感知舒适度有显著影响。例如，较宽的车座鼻部有助于分散压力，而镂空设计则可能在某些情况下改变压力点 55。
骑行姿势与会阴部压迫的关联
除了车座设计，骑行姿势，尤其是车把高度，对会阴部压迫也具有重要影响。
- 车把高度： 一项针对长距离骑行者的研究显示，车把高度与车座高度相对平行或高于车座时，ED的风险显著增加（RR 3.0），而车把高度低于车座时则风险较低 54。这可能是因为车把较高时，骑行者躯干更直立，体重更多地集中在会阴部；而车把较低时，骑行者躯干前倾，一部分体重会通过手臂分散到车把上，从而减轻了车座对会阴部的压力。
- 站立骑行： 短暂的站立骑行可以显著增加阴茎血流，有效缓解会阴部压迫 57。因此，在长时间骑行中，建议定期从坐姿转换为站姿，并适当休息，以避免持续性压迫 5257。
暂时性麻木与长期勃起功能障碍（ED）的风险剂量关系
阴部麻木是骑行者普遍报告的症状，被认为是会阴部神经血管受压的直接表现。研究显示，高达61%的骑行者报告有生殖器区域麻木 52。这种麻木通常是暂时性的，在停止骑行后会逐渐恢复。然而，长期、频繁地经历麻木感，可能预示着潜在的神经血管损伤，进而增加长期ED的风险。
- 麻木与ED的关联： 在长距离骑行者中，骑行过程中出现会阴部麻木与ED的风险显著相关（RR 4.4）54。这表明麻木感可能是ED发展的一个早期警示信号。
- 剂量效应： 研究发现，每周训练距离超过400公里的骑行者中，有19%抱怨出现ED 52。尽管并非所有报告麻木的骑行者都会发展为ED，但麻木的频率、强度和持续时间可能与ED的发生风险存在剂量效应。持续性的麻木表明神经血管持续受到压迫，可能导致更严重的结构性损伤，如阴茎海绵体纤维化，最终影响勃起功能 5253。
- 男性和女性差异： 值得注意的是，会阴部压迫对女性骑行者同样会造成影响，可能导致生殖器麻木和性功能障碍（Female Sexual Dysfunction, FSD），尤其是当麻木部位集中在会阴和外阴时，FSD风险显著增加 5859。虽然有研究指出，男性骑行者报告的生殖器麻木与性健康指数（SHIM）评分（用于评估ED）无显著关联 60，但这可能与研究样本、评估工具和混杂因素控制有关，需要更多高质量研究来进一步确认。
综上所述，骑行中会阴部压迫对男性睾丸健康构成潜在风险，主要表现为阴部麻木和可能引发的ED。车座设计（特别是宽度和对坐骨结节的支撑）、车把高度以及骑行姿势是影响压迫程度的关键因素。骑行者应重视并及时调整这些因素，同时注意在长时间骑行中变换姿势和适当休息，以规避潜在风险。
3.2 阴囊温度升高对睾丸功能的影响
睾丸生精细胞对温度极为敏感，其最佳工作温度通常比核心体温低2-6°C 6162。这种温度差异对于正常的精子发生（spermatogenesis）至关重要。因此，任何导致阴囊局部温度升高的因素，都可能对精子质量和睾丸功能产生负面影响 63。骑行，特别是长时间骑行，因其独特的姿势和装备，被认为可能导致阴囊散热受阻，从而升高局部温度。
阴囊温度升高的机制
骑行时阴囊温度升高主要由以下几个因素引起：
- 紧身裤（特别是骑行裤）： 紧身骑行裤虽然能够减少摩擦，提高舒适度，但其紧密贴合身体的设计可能会限制阴囊的自然悬垂和空气流通，从而阻碍热量散发。这种“绝缘”效应会使阴囊内部温度升高，类似于实验室中用于诱导睾丸热应激的“阴囊绝缘”模型 61。
- 久坐车座： 长时间坐在自行车座上，会使得阴囊持续贴合座面，进一步限制了局部空气流通和热量散发。车座本身的材质和透气性也会影响热量积聚。
- 运动产生的体热： 骑行作为一项体力活动，会产生大量代谢热量，导致核心体温升高。虽然身体会通过排汗等方式散热，但阴囊区域的散热效率可能不足以抵消局部热量积聚。
阴囊温度升高对精子质量的影响
多项研究表明，阴囊温度升高与精子质量下降之间存在明确关联。精子对热应激的敏感性体现在其形态、活力、浓度和DNA完整性等多个方面：
- 精子活力和形态受损： 研究表明，睾丸温度升高会显著降低精子的总活力和前向运动能力，并增加异常精子的比例，特别是头部形态异常的精子 616263。一项对公牛和公羊的研究发现，阴囊绝缘或全身受热导致阴囊皮下温度升高约0.8-2.5°C，从而导致精子总活力和前向运动能力在3-4周内降至低点（分别为20%和10%），形态正常精子和顶体完整性也显著下降 61。
- 精子浓度和DNA损伤： 长期或反复的局部高温可能导致精子生成数量减少，从而降低精子浓度。此外，热应激还会增加精子DNA的损伤，这可能影响受精能力和胚胎发育 6364。
- 氧化应激： 睾丸局部温度升高会加剧活性氧（ROS）的产生，并可能导致抗氧化防御系统失衡，从而引发氧化应激 636465。氧化应激是精子功能障碍和DNA损伤的重要原因之一，因为它会直接攻击精子膜脂、蛋白质和DNA 64。研究发现，睾丸温度升高与精子4-HNE（一种脂质过氧化产物）修饰蛋白的生成呈强相关性，这表明氧化应激与热应激密切相关 64。
- 影响的滞后性： 精子发生周期较长（在人类中约为70-90天），因此，热应激对精子质量的影响往往具有滞后性。一项针对公牛的研究发现，精子质量参数（如运动能力、形态、DNA碎片）与受精前1-2个月的气候因素相关性更高，而非当月气候因素 66。这意味着骑行引起的热应激可能在数周甚至数月后才体现出对精子质量的负面影响。
骑行对阴囊温度影响的临床证据强度
尽管理论上骑行可能导致阴囊温度升高，但现有研究对其影响的临床证据强度并不一致：
- 轻度骑行的影响： 一项研究对25名志愿者进行了60分钟、25瓦功率的适度骑行（约25.45公里/小时），结果显示阴囊温度仅从开始的35.75°C（左侧）和35.50°C（右侧）升高至35.82°C和35.59°C，且未发现骑行时长与阴囊温度之间的相关性。相反，骑行时的阴囊温度甚至显著低于骑行前坐姿状态下最后10分钟的温度（左侧低1.31°C，右侧低1.46°C） 67。这项研究表明，在标准化条件下进行的中等强度骑行并非主要的生殖器热应激因素 67。
- 长期、高强度骑行的潜在影响： 然而，另有研究指出，男性耐力运动员，特别是自行车运动员，可能出现精子活力下降的情况 68。一项早期研究对专业自行车运动员、精英铁人三项运动员和休闲马拉松运动员的精液和激素水平进行了评估，结果发现，尽管各组间的激素水平和精液参数无显著差异，但在比赛期间，自行车运动员的精子活力普遍较低（46.2%），这可能与骑行相关的物理因素（如机械创伤和/或睾丸温度升高）有关 68。
- 内裤类型与睾丸温度： 值得一提的是，关于内裤类型对睾丸温度影响的研究，并未发现平角裤（boxer shorts）与三角裤（briefs）在阴囊温度上存在显著差异，也未发现内裤类型与男性生育力之间存在明确关联 69。这提示，骑行裤对阴囊温度的影响可能更为复杂，需要结合材质、透气性和设计等多种因素综合考虑。
现有证据的局限性
目前关于骑行导致阴囊温度升高对睾丸功能影响的研究，存在以下局限性：
- 研究设计： 多数是观察性研究或小样本实验，缺乏大规模、长期随访的随机对照试验。
- 温度测量： 阴囊温度测量方法多样，准确性、持续性监测能力有待提高。
- 混杂因素： 骑行强度、时长、车座设计、骑行裤材质、环境温度、个体差异（如肥胖 6570、精索静脉曲张等）等均可能影响结果，难以完全控制。例如，肥胖本身就与阴囊温度升高、氧化应激增加及精子质量下降相关 6570。
- 因果关系： 难以明确骑行是精子质量下降的直接原因，还是多种因素（如训练强度、营养、疲劳）共同作用的结果。
总结
尽管适度骑行可能不会显著升高阴囊温度，但长时间、高强度骑行，结合紧身骑行裤和特定车座设计，仍可能导致阴囊局部热量积聚，进而对精子质量产生不利影响，主要表现为精子活力、形态和DNA完整性的受损，以及氧化应激的增加。然而，这些负面影响的临床显著性和普遍性仍需更多高质量研究证实。骑行者应注意选择透气性好的骑行裤，合理安排骑行时长，并考虑车座的舒适度和散热设计，以尽量降低潜在风险。
3.3 骑行相关睾丸损伤的临床证据强度
骑行除了可能通过会阴部压迫和阴囊温度升高影响睾丸健康外，其对睾丸本身，包括曲细精管结构和精索静脉曲张（Varicocele, VCL）进展的潜在影响，也引起了学术界的关注。本节将结合2020年后的动物实验与人体观察性研究，评估这些损伤的临床证据强度。
骑行与睾丸微损伤（如曲细精管结构改变）
睾丸微损伤通常指的是在组织学或细胞学层面上观察到的细微结构变化，这些变化可能在宏观上不明显，但长期累积可能影响生精功能。目前直接将骑行与人类睾丸曲细精管结构改变关联的研究较少，主要证据来源于对运动员的观察性研究或动物模型实验。
在动物模型中，模拟会阴部压迫或热应激的干预可能会导致睾丸组织的微观变化。例如，一些研究通过对小鼠或大鼠的局部压迫或热应激，观察到睾丸间质水肿、生精上皮细胞凋亡增加以及曲细精管结构紊乱的现象。这些变化提示，机械压力和局部高温可能直接作用于生精细胞，影响其正常的生理功能。然而，这些动物实验的结果不能简单推广到人类，因为动物的生理结构、对压力的耐受性以及运动模式与人类存在差异。
对于人体，目前缺乏直接证据表明骑行会导致曲细精管的结构性微损伤。运动员的精液质量下降更多地被归因于综合因素，如过度训练、系统性炎症、氧化应激以及局部温度升高，而非特定微损伤。未来的研究需要通过睾丸活检等侵入性手段来直接观察骑行对人类睾丸微观结构的影响，但这在伦理和可行性上存在挑战。
骑行与精索静脉曲张（VCL）进展的关联性
精索静脉曲张是男性不育的常见原因之一，其特征是阴囊内精索蔓状静脉丛异常扩张、迂曲。传统观念认为，精索静脉曲张的发生与精索内静脉瓣膜功能不全、血管解剖学特征以及直立姿势下重力作用导致的血液回流障碍有关。关于骑行与精索静脉曲张进展的关联性，现有研究的证据强度较为有限且不一致。
理论上，骑行时长时间保持坐姿可能会增加腹腔内压，从而对精索静脉造成一定压力，影响血液回流。此外，骑行引起的阴囊局部温度升高和氧化应激也可能被认为是精索静脉曲张的潜在诱发或加重因素，因为氧化应激是精索静脉曲张导致睾丸功能障碍的重要机制之一 71。精索静脉曲张患者的精浆中氧化应激标志物（如丙二醛，MDA）水平显著升高，且精索静脉曲张切除术后MDA水平会显著下降 72。
然而，目前并没有足够强有力的临床证据直接证明骑行会导致精索静脉曲张的发生或加速其进展。
- 流行病学研究： 多数关于精索静脉曲张的流行病学研究并未将骑行明确列为高风险因素。相反，一些研究甚至认为，孤立的右侧精索静脉曲张与恶性肿瘤相关性极低，无需额外的影像学筛查 73。
- 机制探讨： 虽然有假说认为骑行可能通过增加腹压和局部温度影响精索静脉，但这些机制在精索静脉曲张发病中的作用尚未完全阐明。精索静脉曲张的形成机制复杂，涉及静脉瓣膜缺陷、血管解剖变异、重力及可能存在的遗传因素。骑行本身并不直接改变静脉瓣膜结构。
- 临床干预： 精索静脉曲张的治疗主要通过手术（如精索静脉曲张切除术）来改善精液参数和生育能力，并且手术治疗在特定情况下被证明是有效的 74。但这些手术指征中，骑行并非一项独立的考量因素。
现有证据的局限性
关于骑行对睾丸微损伤和精索静脉曲张影响的研究存在以下局限性：
- 研究设计： 大部分为观察性研究或动物实验，缺乏前瞻性、大样本的随机对照试验，难以建立明确的因果关系。
- 混杂因素： 精索静脉曲张的发生和发展受多种因素影响，包括遗传、年龄、职业、生活习惯等。在研究中难以完全排除这些混杂因素的影响。
- 诊断标准： 精索静脉曲张的诊断主要依赖体格检查和超声多普勒，其程度的评估也存在一定主观性。睾丸微损伤则需要侵入性检查，这限制了在健康人群中的研究。
- 骑行参数： 缺乏对骑行强度、时长、频率、车座类型、骑行姿势等具体参数的标准化和量化分析，这使得不同研究之间难以比较。
总结
综合来看，目前关于骑行导致男性睾丸微损伤（如曲细精管结构改变）和精索静脉曲张进展的临床证据强度相对较弱。尽管理论上长时间的会阴部压迫和局部温度升高可能对睾丸功能产生不利影响，但尚未有确凿证据表明骑行是这些病理改变的直接或主要原因。未来的研究应侧重于更大规模、更精细化的临床研究，并结合生物标志物和影像学技术，以更准确地评估骑行对男性睾丸健康的长期影响。在此之前，骑行爱好者无需过度担忧，但仍应重视骑行姿势、装备选择和适当休息，以最大程度降低潜在风险。
4. 风险规避与效率优化：基于证据的骑行建议
4.1 骑行装备与姿势的优化策略
为了最大限度地发挥骑行作为锻炼方式的健康效益，同时规避潜在的脊柱和男性睾丸健康风险，科学地选择骑行装备和优化骑行姿势至关重要。基于生物力学与临床研究的证据，以下将详细阐述车座选择、车把高度调整和骑行裤设计等方面的优化策略。
4.1.1 车座选择：宽度、材质与设计
车座是骑行者与自行车最主要的接触点，其设计对会阴部压力和脊柱舒适度有着决定性影响。
- 车座宽度： 研究表明，选择与骑行者坐骨结节（ischial tuberosity）宽度相匹配或略宽（例如超出1厘米）的车座，能够有效改善座压分布，将身体重量更多地分散到坐骨上，而非会阴部软组织。这对于女性骑行者尤为重要，因为她们的坐骨宽度通常大于男性 7576。宽型车座有助于减少会阴部的最大和平均压力，降低对阴部神经和血管的压迫，从而减轻麻木感 75。
- 车座材质与填充： 虽然车座填充物的软硬程度对舒适度有一定影响，但研究表明其对会阴部压力的减轻效果不如车座宽度显著。过软的车座可能导致坐骨下陷，反而使会阴部承受更多压力。因此，选择具有适当支撑性和弹性的材质更为关键。透气性好的材质有助于局部散热，进一步降低阴囊温度升高带来的风险。
- 车座设计（有无镂空/短鼻座）： 对于传统车座而言，带有中央镂空或凹槽设计的车座旨在减轻会阴部压力。然而，正如前文所述，其效果因人而异，某些情况下可能导致压力重新分布到镂空边缘，反而加剧局部压迫。对于男性骑行者，"无鼻座"（no-nose saddle）或短鼻座已被证实能显著降低会阴部压力和提高阴茎供氧量，有效减少会阴部麻木和改善勃起功能 7778。但无鼻座可能牺牲一定的操控稳定性，这需要骑行者在使用中进行权衡和适应。对于女性骑行者，宽且带有部分鼻部镂空的设计可能是一个较好的折衷方案，它既能重新分配座压，又可能避免显著增加会阴部不适，尽管在某些情况下可能会增加坐骨结节不适 55。
4.1.2 车把高度与骑行姿势调整
车把的高度和与车座的相对位置，直接决定了骑行者的躯干前倾角度和骨盆倾斜度，进而影响脊柱负荷和会阴部压力。
- 车把高度调整： 将车把高度调整至略低于车座（通常建议低于车座5-10厘米），可以促使骑行者躯干前倾。这种姿势能将部分体重通过手臂传递到车把上，从而减轻车座对会阴部的垂直压力，降低阴部神经受压的风险。然而，过度前倾的姿势可能增加腰椎的屈曲度，对腰椎间盘造成更大压力，并可能引起颈部和肩部不适。因此，需要根据个体柔韧性、核心力量和骑行类型（如休闲骑行、公路竞赛）进行个性化调整。
- 核心肌群强化： 无论何种骑行姿势，强大的核心肌群是维持脊柱稳定、减轻脊柱压力的关键。核心力量训练能够帮助骑行者在长时间前倾姿势下保持脊柱的生理曲度，有效避免腰椎过度屈曲。这对于预防和缓解骑行相关低背痛至关重要。
- 骑行中姿势变换： 长时间保持同一姿势容易导致局部压力集中和肌肉疲劳。建议在长距离骑行中，每隔一段时间（例如每10-15分钟）变换手部握把位置，或短暂站立蹬踏几秒钟，以改变会阴部和脊柱的受力点，促进血液循环，减轻局部压力 77。
4.1.3 骑行裤设计：透气与减震
骑行裤的设计对会阴部舒适度和局部温度有直接影响。
- 透气垫（Chamois）： 专业的骑行裤通常集成有高品质的透气垫。透气垫的主要功能是提供减震、减少摩擦，并吸收汗液，从而提高骑行舒适度。选择具有良好透气性和排湿功能的垫子，有助于保持会阴部区域的干爽，减少局部热量积聚，降低阴囊温度升高的风险。
- 材质： 骑行裤的材质应选择具有良好透气性、排汗性和速干性的面料，如合成纤维或特殊混纺面料。避免穿着过紧或不透气的普通内裤，因为这会阻碍局部散热，增加潮湿和感染的风险。
通过对车座、车把和骑行裤的合理选择与调整，骑行者可以显著优化骑行姿态，降低脊柱负荷和会阴部压迫，从而规避潜在的健康风险，使骑行成为一种更安全、更舒适、更高效的锻炼方式。
4.2 运动强度与频率的科学调控
科学地调控骑行的运动强度与频率，是平衡锻炼效率与身体组织耐受阈值的关键，对于实现最佳健康收益并避免过度训练或损伤至关重要。运动医学指南和长期追踪研究为不同人群的骑行处方提供了依据。
4.2.1 运动强度的评估与建议
运动强度通常可以通过心率（最大心率百分比）、代谢当量（METs）、感知运动强度（RPE）或功率输出等指标进行量化。
最大心率百分比（%HRmax）： 这是最常用的强度评估方法之一。一般而言，中等强度运动的目标心率范围是最大心率的60%-75%，高强度运动则在75%-90%之间。
- 健康成人： 对于寻求改善心肺健康的健康成人，建议进行中等强度（60%-75% HRmax）骑行，或结合高强度（75%-90% HRmax）间歇训练。高强度间歇训练（HIIT）在短时间内被证明能够有效提升VO₂max和运动表现 79。例如，在慢性阻塞性肺疾病（COPD）患者中，恒定功率骑行耐力时间被证实是评估运动耐力有效且可行的指标，其最低重要差异约为1分钟，这提示了运动强度与耐力间的量化关系 80。
- 慢性病患者： 对于高血压患者，骑行作为一种有氧运动，有助于降低血压和改善心血管健康 81。建议从较低强度开始（例如50%-60% HRmax），并根据身体反应逐渐增加。2型糖尿病患者进行中等强度骑行能有效改善血糖控制和心肺适能。
- 运动员： 竞技运动员的强度调控更为精细，常结合功率计数据、乳酸阈值、以及心率变异性来优化训练负荷，以期在不导致过度训练的前提下，最大化运动表现 79。
感知运动强度（RPE）： 对于没有心率监测设备或不熟悉心率区间的个体，RPE量表（Borg RPE量表，6-20分）是一个简便有效的工具。中等强度通常对应RPE 12-14（感觉有点吃力），高强度对应RPE 15-17（感觉很吃力）。
4.2.2 运动频率与时长的建议
- 频率： 大多数运动指南推荐健康成人每周进行3-5次有氧运动。对于骑行，这意味着每周至少3次骑行，以确保足够的训练刺激来引发生理适应。
- 时长：
- 单次骑行： 对于健康成人，建议单次骑行时长控制在30-90分钟。长时间（例如超过2小时）的持续骑行，尤其是对于尚未完全适应的个体，可能会增加肌肉疲劳、关节不适以及会阴部压迫的风险。有研究指出，男性骑行者每周骑行超过400公里可能与勃起功能障碍风险增加有关。因此，建议适当控制单次骑行时长，并在长时间骑行中安排休息和姿势变换。
- 每周总时长： 根据美国运动医学会（ACSM）的建议，每周至少150分钟的中等强度有氧运动，或75分钟的高强度有氧运动，即可带来显著的健康益处。对于骑行，这意味着每周累计2.5-5小时的骑行时间。
- 循序渐进原则： 无论何种人群，都应遵循循序渐进的原则。不应突然大幅增加骑行时长、频率或强度，应给予身体足够的时间去适应新的训练负荷，以降低运动损伤的风险。
4.2.3 锻炼效率与组织耐受阈值的平衡
- 负荷管理： 科学的运动处方强调个体化和周期化。运动负荷（强度 × 频率 × 时长）应根据个体的健康状况、训练水平和目标进行调整。过低的负荷可能无法带来足够的生理刺激，而过高的负荷则可能导致过度训练、免疫功能下降、慢性疲劳甚至运动损伤。例如，研究表明，过度训练和过度使用损伤是竞技骑行者常见的健康问题 79。
- 恢复： 充分的恢复是训练成功的关键组成部分。这包括充足的睡眠、均衡的营养以及主动恢复（如低强度骑行或伸展）。在训练计划中加入休息日或低强度训练日，让身体有时间修复和适应。
- 身体信号： 倾听身体的信号至关重要。如果出现持续性疲劳、肌肉或关节疼痛、睡眠质量下降、食欲不振等症状，可能是身体发出需要休息的信号。及时调整训练计划，避免过度疲劳，有助于长期坚持骑行锻炼。
- 交叉训练： 对于专业骑行者，将力量训练融入训练计划中，可以增强肌肉力量和质量，提高骑行表现，并降低受伤风险 82。对于普通骑行爱好者，结合力量训练（特别是核心肌群和下肢力量）和柔韧性训练，可以弥补骑行在肌肉激活范围上的局限性，从而更全面地促进身体健康，降低LBP等风险。
通过对运动强度、频率和时长的科学调控，骑行者可以在实现心肺功能提升、能量消耗、脂肪减少等健康目标的同时，最大限度地降低潜在的健康风险，确保长期、持续地从骑行中获益。
4.3 特殊人群的骑行适应性管理
针对特定健康状况或特殊需求的个体，骑行运动需要进行个性化的适应性管理，以最大限度地发挥其康复和健康促进作用，同时规避潜在风险。这包括结合康复医学与运动处方研究，为脊髓损伤、腰椎退行性病变和精索静脉曲张患者提供定制化的骑行方案。
4.3.1 脊髓损伤患者的骑行方案
脊髓损伤（SCI）患者常伴有下肢瘫痪、骨密度下降、肌肉萎缩及心血管功能受损等问题。功能性电刺激骑行（FES-cycling）是为这类患者量身定制的有效干预手段。
- FES-cycling 的应用： FES-cycling 通过电刺激瘫痪的肌肉群，使其产生节律性收缩，从而带动自行车踏板转动。这不仅能提供心血管益处，还能有效逆转肌肉萎缩，并在一定程度上提高骨密度，降低骨折风险。
- 方案制定： 具体的FES-cycling方案需在专业康复医师和物理治疗师指导下进行。强度和时长应根据患者的神经功能水平、肌肉耐受性和心血管状况逐步调整。
- 监测与评估： 训练过程中需密切监测患者的生理反应，包括心率、血压、血氧饱和度及有无肌肉疲劳或痉挛。定期评估心肺功能、肌肉力量和骨密度变化，以调整训练计划。
- 结合辅助技术： 对于完全性SCI患者，FES-cycling是主要的运动方式。对于不完全性SCI患者，可将FES-cycling与传统物理治疗、步态训练等结合，以促进神经可塑性和功能恢复。
4.3.2 腰椎退行性病变患者的骑行方案
腰椎退行性病变（如椎间盘突出、椎管狭窄、骨关节炎）患者在进行骑行时需格外注意，以避免加重脊柱负担。
- 车身设置调整：
- 直立骑行姿势： 相比公路车，选择城市通勤车或休闲自行车，其车把通常较高且靠近车座，使骑行者能保持更直立的坐姿，减少腰椎前屈，从而降低对椎间盘的压力。
- 车把高度： 建议将车把设置在与车座等高或略高于车座的位置，避免躯干过度前倾。
- 车座选择： 选择宽大、支撑性好且能有效支撑坐骨的车座，以分散体重，减少脊柱负荷。
- 运动强度与时长：
- 低到中等强度： 避免高强度冲刺或需要剧烈躯干扭转的骑行。建议进行低到中等强度的有氧骑行，以达到心肺锻炼效果而不给脊柱带来过大压力。
- 控制时长： 单次骑行时长不宜过长，建议不超过60分钟。在长时间骑行中，应定期下车活动，进行伸展和放松。
- 核心肌群强化： 核心肌群是稳定脊柱的关键。腰椎退行性病变患者应在日常生活中加强核心力量训练，如普拉提、平板支撑等，以提高脊柱的稳定性，辅助骑行时维持正确姿势。有研究表明，对于慢性非特异性腰痛患者，特定躯干练习能够有效减轻疼痛和残疾，这对于骑行者同样具有指导意义。
- 症状监测： 在骑行过程中，如出现腰痛加剧、腿部麻木或放射痛等症状，应立即停止骑行并休息，必要时寻求医疗专业人士的指导。
4.3.3 精索静脉曲张患者的骑行方案
精索静脉曲张患者在骑行时应关注阴囊局部温度和会阴部压迫，以避免潜在的加重因素。
- 车座选择：
- 宽大、透气车座： 选择宽度合适、能有效支撑坐骨的车座，避免对会阴部软组织造成持续压迫。考虑选用具有良好透气性的车座，以促进局部散热。
- 避免过度压迫型车座： 尽管镂空车座能减轻局部压力，但其效果因人而异。对于精索静脉曲张患者，更应关注整体的压力分散和舒适度，避免任何可能加重会阴部或阴囊局部压迫的设计。
- 骑行裤选择： 穿着宽松、透气性好的骑行裤，避免过于紧身或不透气的材质，以确保阴囊区域的良好通风和散热。
- 运动强度与频率：
- 避免过热： 尽管有研究表明适度骑行对阴囊温度影响不大，但长时间、高强度骑行，尤其是在炎热环境下，仍可能导致阴囊温度升高。建议精索静脉曲张患者避免在高温环境下长时间骑行，并注意骑行过程中的降温。
- 适度休息： 长时间骑行过程中，应定期下车休息，变换姿势，让阴囊有充分的空气流通和降温机会。
- 症状监测： 患者应注意监测精索静脉曲张症状（如阴囊坠胀感、疼痛）的变化。若骑行后症状加重，应及时调整骑行方式或寻求泌尿科医生的专业建议。
通过上述精细化管理，特殊人群可以安全有效地参与骑行运动，从而改善整体健康状况，提高生活质量。关键在于个性化的评估、科学的处方和持续的监测。
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参考文献
1Determining the intensity and energy expenditure during commuter cycling.PubMed
B de Geus, S De Smet, J Nijs, et al.
Br J Sports Med. 2007 Jan;41(1):8-12. doi: 10.1136/bjsm.2006.027615. Epub 2006 Oct 4.
OBJECTIVES: To determine the intensity and energy expenditure during commuter cycling, and to investigate whether cycling to work at a self-chosen intensity corresponds to recommendations of the Centers for Disease Control and Prevention (CDC) and American College of Sports Medicine (ACSM) for health improvement and ACSM recommendations for fitness improvement. METHODS: 18 healthy, untrained middle-aged people, who did not cycle to work, underwent two maximal exercise tests (MT and MT2) in order to measure their maximal heart rate and oxygen consumption (VO(2)). MT2 was performed 24 weeks after MT. Participants were asked to cycle at least three times a week to their workplace over a one-way minimum distance of 2 km. Data on cycling were recorded in a diary. 12 weeks after MT, a field test was conducted, where participants had to cycle to or from their workplace. The same measurements were taken as during MT as markers of exercise intensity. Metabolic equivalents (METs) and energy expenditure were calculated. RESULTS: The intensity during the field test was >75% of their maximal aerobic capacity. The mean (SD) MET value was 6.8 (1.9). The energy expenditure during the field test was 220 (115) kcal or 540 (139) kcal/h and 1539 (892) kcal/week. Men consumed significantly (p<0.01) more energy per hour than women. CONCLUSION: Commuter cycling at a self-selected intensity meets the CDC and ACSM recommendations for health improvement and the ACSM recommendations for improvement of cardiorespiratory fitness. However, as the participants cycled faster during the field test than during daily cycling, the results should be interpreted with caution.
2Optimizing fat oxidation through exercise and diet.PubMed
Juul Achten, Asker E Jeukendrup
Nutrition. 2004 Jul-Aug;20(7-8):716-27. doi: 10.1016/j.nut.2004.04.005.
Interventions aimed at increasing fat metabolism could potentially reduce the symptoms of metabolic diseases such as obesity and type 2 diabetes and may have tremendous clinical relevance. Hence, an understanding of the factors that increase or decrease fat oxidation is important. Exercise intensity and duration are important determinants of fat oxidation. Fat oxidation rates increase from low to moderate intensities and then decrease when the intensity becomes high. Maximal rates of fat oxidation have been shown to be reached at intensities between 59% and 64% of maximum oxygen consumption in trained individuals and between 47% and 52% of maximum oxygen consumption in a large sample of the general population. The mode of exercise can also affect fat oxidation, with fat oxidation being higher during running than cycling. Endurance training induces a multitude of adaptations that result in increased fat oxidation. The duration and intensity of exercise training required to induce changes in fat oxidation is currently unknown. Ingestion of carbohydrate in the hours before or on commencement of exercise reduces the rate of fat oxidation significantly compared with fasted conditions, whereas fasting longer than 6 h optimizes fat oxidation. Fat oxidation rates have been shown to decrease after ingestion of high-fat diets, partly as a result of decreased glycogen stores and partly because of adaptations at the muscle level.
3Endurance exercise performance: the physiology of champions.PubMed
Michael J Joyner, Edward F Coyle
J Physiol. 2008 Jan 1;586(1):35-44. doi: 10.1113/jphysiol.2007.143834. Epub 2007 Sep 27.
Efforts to understand human physiology through the study of champion athletes and record performances have been ongoing for about a century. For endurance sports three main factors--maximal oxygen consumption (.VO(2,max)), the so-called 'lactate threshold' and efficiency (i.e. the oxygen cost to generate a given running speed or cycling power output)--appear to play key roles in endurance performance. and lactate threshold interact to determine the 'performance .VO(2)' which is the oxygen consumption that can be sustained for a given period of time. Efficiency interacts with the performance .VO(2) to establish the speed or power that can be generated at this oxygen consumption. This review focuses on what is currently known about how these factors interact, their utility as predictors of elite performance, and areas where there is relatively less information to guide current thinking. In this context, definitive ideas about the physiological determinants of running and cycling efficiency is relatively lacking in comparison with .VO(2,max) and the lactate threshold, and there is surprisingly limited and clear information about the genetic factors that might pre-dispose for elite performance. It should also be cautioned that complex motivational and sociological factors also play important roles in who does or does not become a champion and these factors go far beyond simple physiological explanations. Therefore, the performance of elite athletes is likely to defy the types of easy explanations sought by scientific reductionism and remain an important puzzle for those interested in physiological integration well into the future.
4Physiological differences between cycling and running: lessons from triathletes.PubMed
Gregoire P Millet, V E Vleck, D J Bentley
Sports Med. 2009;39(3):179-206. doi: 10.2165/00007256-200939030-00002.
The purpose of this review was to provide a synopsis of the literature concerning the physiological differences between cycling and running. By comparing physiological variables such as maximal oxygen consumption (V O(2max)), anaerobic threshold (AT), heart rate, economy or delta efficiency measured in cycling and running in triathletes, runners or cyclists, this review aims to identify the effects of exercise modality on the underlying mechanisms (ventilatory responses, blood flow, muscle oxidative capacity, peripheral innervation and neuromuscular fatigue) of adaptation. The majority of studies indicate that runners achieve a higher V O(2max) on treadmill whereas cyclists can achieve a V O(2max) value in cycle ergometry similar to that in treadmill running. Hence, V O(2max) is specific to the exercise modality. In addition, the muscles adapt specifically to a given exercise task over a period of time, resulting in an improvement in submaximal physiological variables such as the ventilatory threshold, in some cases without a change in V O(2max). However, this effect is probably larger in cycling than in running. At the same time, skill influencing motor unit recruitment patterns is an important influence on the anaerobic threshold in cycling. Furthermore, it is likely that there is more physiological training transfer from running to cycling than vice versa. In triathletes, there is generally no difference in V O(2max) measured in cycle ergometry and treadmill running. The data concerning the anaerobic threshold in cycling and running in triathletes are conflicting. This is likely to be due to a combination of actual training load and prior training history in each discipline. The mechanisms surrounding the differences in the AT together with V O(2max) in cycling and running are not largely understood but are probably due to the relative adaptation of cardiac output influencing V O(2max) and also the recruitment of muscle mass in combination with the oxidative capacity of this mass influencing the AT. Several other physiological differences between cycling and running are addressed: heart rate is different between the two activities both for maximal and submaximal intensities. The delta efficiency is higher in running. Ventilation is more impaired in cycling than in running. It has also been shown that pedalling cadence affects the metabolic responses during cycling but also during a subsequent running bout. However, the optimal cadence is still debated. Central fatigue and decrease in maximal strength are more important after prolonged exercise in running than in cycling.
5Training for intense exercise performance: high-intensity or high-volume training?PubMed
P B Laursen
Scand J Med Sci Sports. 2010 Oct;20 Suppl 2:1-10. doi: 10.1111/j.1600-0838.2010.01184.x.
Performance in intense exercise events, such as Olympic rowing, swimming, kayak, track running and track cycling events, involves energy contribution from aerobic and anaerobic sources. As aerobic energy supply dominates the total energy requirements after ∼75s of near maximal effort, and has the greatest potential for improvement with training, the majority of training for these events is generally aimed at increasing aerobic metabolic capacity. A short-term period (six to eight sessions over 2-4 weeks) of high-intensity interval training (consisting of repeated exercise bouts performed close to or well above the maximal oxygen uptake intensity, interspersed with low-intensity exercise or complete rest) can elicit increases in intense exercise performance of 2-4% in well-trained athletes. The influence of high-volume training is less discussed, but its importance should not be downplayed, as high-volume training also induces important metabolic adaptations. While the metabolic adaptations that occur with high-volume training and high-intensity training show considerable overlap, the molecular events that signal for these adaptations may be different. A polarized approach to training, whereby ∼75% of total training volume is performed at low intensities, and 10-15% is performed at very high intensities, has been suggested as an optimal training intensity distribution for elite athletes who perform intense exercise events.
6Correlates of Heart Rate Measures with Incidental Physical Activity and Cardiorespiratory Fitness in Overweight Female Workers.PubMed
Laís Tonello, Felipe F Reichert, Iransé Oliveira-Silva, et al.
Front Physiol. 2016 Jan 7;6:405. doi: 10.3389/fphys.2015.00405. eCollection 2015.
Previous studies have suggested that physical activity (PA) levels and cardiorespiratory fitness (CRF) impact on the autonomic control of heart rate (HR). However, previous studies evaluating PA levels did not discriminate between incidental PA and regular exercise. We hypothesized that incidental PA "per se" would influence cardiac autonomic indices as assessed via HR variability (HRV) and HR recovery (HRR) in non-exercisers. Thus, the objective of this study was to investigate the relationships between objective PA levels, CRF, and cardiac autonomic indices in adult, regular non-exercising female workers. After familiarization with procedures and evaluation of body composition, 21 women completed a submaximal cycling test and evaluation of HRR on four different days. Resting (2-min seated and standing) and ambulatory (4-h) HRV were also recorded. Levels of PA were assessed by accelerometry over five consecutive days (i.e., Wednesday to Sunday). Maximum oxygen consumption (VO2max) was measured as an index of CRF. As reliability was low to moderate for most HR measures, relationships between these and PA and CRF were examined using the 4-day average measures. Significant correlations were identified between post-exercise HRR in the first min with various PA indices (daily moderate PA, daily vigorous PA, and the sum of vigorous and very vigorous daily PA). Additionally, VO2max was significantly correlated to HRV but not to HRR. The current results indicated that CRF was influential in enhancing HRV while incidental or non-exercise based PA was associated with greater autonomic reactivation in adult overweight women. Therefore, both CRF and non-exercise based PA contribute significant but diverse effects on cardiac health. The use of 4-day averages instead of single measures for evaluation of autonomic control of HR may provide a better indication of regular cardiac autonomic function that remains to be refined.
7[Effect of ultra-endurance swimming on body composition--marathon swim 2006 from Rapperswil to Zurich].PubMed
B Knechtle, B Baumann, P Knechtle
Praxis (Bern 1994). 2007 Apr 11;96(15):585-9. doi: 10.1024/1661-8157.96.15.585.
We measured, during a marathon swimming event 2006 in the lake of Zurich, load intensity, energy intake, energy expenditure and impact on both muscle and fat mass in a trained long-distance swimmer. The swimmer had a load intensity of 125 bpm corresponding to 51% VO2(max). Despite adequate energy intake during the load, an energy deficit of 500 kcal per hour occurred, which resulted in a loss of 1.1 kg body mass within 9 hours of swimming.
8Twenty-four-hour energy expenditure and its components in prepubertal children as determined by whole-body indirect calorimetry and compared with young adults.PubMed
A Bitar, M Vermorel, N Fellmann, et al.
Am J Clin Nutr. 1995 Aug;62(2):308-15. doi: 10.1093/ajcn/62.2.308.
The aim of the present study was to compare total daily and circadian variations of energy expenditure (EE) in 21 prepubescent 10-y-old children (12 boys and 9 girls) and 18 23-y-old adults (9 men and 9 women) under the same conditions by using two large calorimetric chambers. The volunteers followed similar activity programs with four periods of exercise on a cyclergometer. Total daily and sleeping EE adjusted for differences in fat-free mass (FFM) and age were significantly higher in children than in adults by 35% and 27%, respectively (P < 0.001). EE during sleep decreased by 2% per hour in both age groups. Heart rate was significantly higher in girls than in boys. The energy cost of cycling, adjusted for differences in FFM and external mechanical power, was not significantly different in children and adults. The differences in EE between children and adults may partly result from a higher proportion of internal organs in the FFM.
9Different exercise training modalities produce similar endothelial function improvements in individuals with prehypertension or hypertension: a randomized clinical trial Exercise, endothelium and blood pressure.PubMed
Marinei L Pedralli, Rafael A Marschner, Daniel P Kollet, et al.
Sci Rep. 2020 May 6;10(1):7628. doi: 10.1038/s41598-020-64365-x.
Endothelial dysfunction is a characteristic of systemic arterial hypertension (SAH) and an early marker of atherosclerosis. Aerobic exercise training (AT) improves endothelial function. However, the effects of resistance training (RT) and combined training (CT) on endothelial function remain controversial in individuals with SAH. We determined the effects of AT, RT, and CT on endothelial function and systolic (SBP)/diastolic blood pressure (DBP) in individuals with prehypertension or hypertension. Forty-two participants (54 ± 11 y, resting SBP/DBP 137 ± 9/86 ± 6 mmHg) were randomly allocated into AT (n = 14, 40 min of cycling, 50-75% heart rate reserve), RT (n = 14, 6 resistance exercises, 4 × 12 repetitions, 60% maximum strength) and CT (n = 14, 2 × 12 repetitions of RT + 20 min of AT). All participants performed a 40-minute exercise session twice a week for 8 weeks. Endothelial function was evaluated by brachial artery flow-mediated dilation (FMD). Blood pressure was evaluated through ambulatory monitoring for 24 hours. After 8 weeks of exercise training, blood pressure was reduced in all 3 groups: -5.1 mmHg in SBP (95%CI -10.1, 0.0; p = 0.003) in AT; -4.0 mmHg in SBP (95%CI -7.8, -0.5; p = 0.027) in RT; and -3.2 mmHg in DBP (95%CI -7.9, 1.5; p = 0.001) in CT. All 3 exercise training modalities produced similar improvements in FMD: + 3.2% (95%CI 1.7, 4.6) (p < 0.001) in AT; + 4.0% (95%CI 2.1, 5.7) (p < 0.001) in RT; and +6.8% (95%CI 2.6, 11.1) (p = 0.006) in CT. In conclusion, different exercise training modalities were similarly effective in improving endothelial function but impacts on ambulatory blood pressure appear to be variable in individuals with prehypertension or hypertension.
10Development of a behavioural support intervention for e-bike use in Australia.PubMed
Jenna McVicar, Rebecca Nourse, Michelle A Keske, et al.
BMC Public Health. 2022 Dec 21;22(1):2399. doi: 10.1186/s12889-022-14693-6.
BACKGROUND: Insufficient physical activity (PA) is a risk factor for the development of many non-communicable diseases. Electric bicycles (e-bikes) offer considerable potential to support people to be physically active, however, no previous e-bike intervention studies have supported e-bike use with behavioural support. The aim of this study was to co-develop theory-based intervention components which can be used to increase physical activity through e-cycling among people who are overweight or obese and physically inactive. METHODS: We conducted a mixed-methods study using an online survey and virtual co-design workshops. We utilised the Behaviour Change Wheel (BCW) to inform the development of the behavioural support intervention to facilitate day-to-day e-cycling. RESULTS: One hundred participants completed an online survey and seven participated in the online co-design workshops. The development of the intervention identified five intervention functions (enablement, training, environmental restructuring, education, and persuasion) and 16 behaviour change techniques (BCTs) from 11 BCT groups (goals and planning, feedback and monitoring, social support, shaping knowledge, natural consequences, comparison of behaviour, associations, repetition and substitution, comparison of outcomes, antecedents, and self-belief). CONCLUSION: To our knowledge, this is the first study to combine co-design and the BCW to develop a comprehensive behavioural support intervention for e-bike use. Theory based intervention options should be considered when providing e-bikes to individuals to help them increase their habitual PA levels.
11Systematic review and meta-analysis evaluating the effects electric bikes have on physiological parameters.PubMed
Jenna McVicar, Michelle A Keske, Reza Daryabeygi-Khotbehsara, et al.
Scand J Med Sci Sports. 2022 Jul;32(7):1076-1088. doi: 10.1111/sms.14155. Epub 2022 Mar 23.
BACKGROUND: There is a universal need to increase the number of adults meeting physical activity (PA) recommendations to help improve health. In recent years, electrically assisted bicycles (e-bikes) have emerged as a promising method for supporting people to initiate and maintain physical activity levels. To the best of our knowledge, there have been no meta-analyses conducted to quantify the difference in physiological responses between e-cycling with electrical assistance, e-cycling without assistance, conventional cycling, and walking. METHODS: A systematic review and meta-analysis was conducted following PRISMA guidelines. We identified short-term e-bike studies, which utilized a crossover design comparing physiological outcomes when e-cycling with electrical assistance, e-cycling without electrical assistance, conventional cycling, or walking. Energy expenditure (EE), heart rate (HR), oxygen consumption (VO ), power output (PO), and metabolic equivalents (METs) outcomes were included within the meta-analysis. RESULTS: Fourteen studies met our inclusion criteria (N = 239). E-cycling with electrical assistance resulted in a lower energy expenditure (EE) [SMD = -0.46 (-0.98, 0.06), p = 0.08], heart rate (HR) [MD = -11.41 (-17.15, -5.68), p < 0.000, beats per minute], oxygen uptake (VO ) [SMD = -0.57 (-0.96, -0.17), p = 0.005], power output (PO) [MD = -31.19 (-47.19 to -15.18), p = 0.000, Watts], and metabolic equivalent (MET) response [MD = -0.83 (-1.52, -0.14), p = 0.02, METs], compared with conventional cycling. E-cycling with moderate electrical assistance resulted in a greater HR response [MD 10.38 (-1.48, 22.23) p = 0.09, beats per minute], and VO response [SMD 0.34 (-0.14, 0.82) p = 0.16] compared with walking. CONCLUSIONS: E-cycling was associated with increased physiological responses that can confer health benefits.
12Physical activity when riding an electric-assisted bicycle with and without cargo.PubMed
Jørgen Jerstad Martnes, Elling Bere
Front Sports Act Living. 2023 Jun 30;5:1179043. doi: 10.3389/fspor.2023.1179043. eCollection 2023.
BACKGROUND: Regular physical activity provides several health benefits, and active transport is a convenient way to implement physical activity in everyday life. However, bikes' lack of possibilities to carry cargo is a limitation. E-cargo bikes can help overcome barriers to cycling and increase levels of active transport while still providing the option to carry cargo such as groceries and children. As such, E-cargo bikes have a greater potential for being a substitute for cars, but relevance is not known as no study has assessed the energy expenditure and time used using E-cargo bikes with considerable cargo. OBJECTIVES: The aim of this study is to compare time spent riding and exercise intensity when (1) riding an electric-assisted bicycle with cargo (30 kg) and without cargo and (2) driving a car. METHOD: This study has a randomised crossover design. Eleven participants (six women) were recruited through convenience sampling. The participants traversed through a 4.5 km route with three different forms of transportation: an electric-assisted bicycle (E-bike) with 30 kg cargo, an E-bike without cargo, and a car. Oxygen uptake was measured with a portable oxygen analyser (Metamax 3B), and time spent cycling was measured on site by the test leader using a stopwatch. RESULTS: Riding an E-bike with cargo was slightly slower than riding an E-bike without cargo (11.8 vs. 11.1 min, = 0.017) and driving a car (8.8 min, = 0.002). There was no significant difference in exercise intensity between E-bikes with and without cargo but riding an E-bike with cargo entailed significantly higher exercise intensity compared to driving a car [4.9 metabolic equivalents of task (METs) vs. 1.4 METs, ≤ 0.001]. CONCLUSIONS: E-biking with cargo was rather similar in time spent and exercise intensity to E-biking without cargo, and not much slower than driving a car. Using E-cargo bikes, therefore, appears a good alternative to driving a car when in need of carrying things such as grocery bags and children, resulting in increasing physical activity and, at the same time, decreasing greenhouse gas emissions.
13Everyday Pedelec Use and Its Effect on Meeting Physical Activity Guidelines.PubMed
Hedwig T Stenner, Johanna Boyen, Markus Hein, et al.
Int J Environ Res Public Health. 2020 Jul 3;17(13):4807. doi: 10.3390/ijerph17134807.
Pedelecs (e-bikes with electrical support up to 25 km·h) are important in active transportation. Yet, little is known about physiological responses during their everyday use. We compared daily pedelec (P) and bicycle (B) use to determine if pedelecs are a suitable tool to enhance physical activity. In 101 employees, cycling duration and intensity, heart rate (HR) during P and B were recorded via a smartphone app. Each recording period was a randomized crossover design and lasted two weeks. The ride quantity was higher in P compared to B (5.3 ± 4.3 vs. 3.2 ± 4.0 rides·wk; < 0.001) resulting in a higher total cycling time per week for P (174 ± 146 min·wk) compared to B (99 ± 109 min·wk; < 0.001). The mean HR during P was lower than B (109 ± 14 vs. 118 ± 17 bpm; < 0.001). The perceived exertion was lower in P (11.7 ± 1.8 vs. 12.8 ± 2.1 in B; < 0.001). The weekly energy expenditure was higher during P than B (717 ± 652 vs. 486 ± 557 metabolic equivalents of the task [MET]·min·wk; < 0.01). Due to a sufficient HR increase in P, pedelecs offer a more active form of transportation to enhance physical activity.
14Health benefits of electrically-assisted cycling: a systematic review.PubMed
Jessica E Bourne, Sarah Sauchelli, Rachel Perry, et al.
Int J Behav Nutr Phys Act. 2018 Nov 21;15(1):116. doi: 10.1186/s12966-018-0751-8.
BACKGROUND: Electrically assisted bicycles (e-bikes) have been highlighted as a method of active travel that could overcome some of the commonly reported barriers to cycle commuting. The objective of this systematic review was to assess the health benefits associated with e-cycling. METHOD: A systematic literature review of studies examining physical activity, cardiorespiratory, metabolic and psychological outcomes associated with e-cycling. Where possible these outcomes were compared to those from conventional cycling and walking. Seven electronic databases, clinical trial registers, grey literature and reference lists were searched up to November 2017. Hand searching occurred until June 2018. Experimental or observational studies examining the impact of e-cycling on physical activity and/or health outcomes of interest were included. E-bikes used must have pedals and require pedalling for electric assistance to be provided. RESULTS: Seventeen studies (11 acute experiments, 6 longitudinal interventions) were identified involving a total of 300 participants. There was moderate evidence that e-cycling provided physical activity of at least moderate intensity, which was lower than the intensity elicited during conventional cycling, but higher than that during walking. There was also moderate evidence that e-cycling can improve cardiorespiratory fitness in physically inactive individuals. Evidence of the impact of e-cycling on metabolic and psychological health outcomes was inconclusive. Longitudinal evidence was compromised by weak study design and quality. CONCLUSION: E-cycling can contribute to meeting physical activity recommendations and increasing physical fitness. As such, e-bikes offer a potential alternative to conventional cycling. Future research should examine the long-term health impacts of e-cycling using rigorous research designs.
15Electrically assisted cycling for individuals with type 2 diabetes mellitus: a pilot randomized controlled trial.PubMed
Jessica E Bourne, Sam Leary, Angie Page, et al.
Pilot Feasibility Stud. 2023 Apr 18;9(1):60. doi: 10.1186/s40814-023-01283-5.
BACKGROUND: Type 2 diabetes mellitus (T2DM) and its associated complications puts considerable strain on healthcare systems. With the global incidence of T2DM increasing, effective disease management is essential. Physical activity (PA) is a key component of T2DM management; however, rates of PA engagement are low in this population. Developing effective and sustainable interventions that encourage PA is a high priority. Electrically assisted bicycles are becoming increasingly popular and may increase PA in healthy adults. This study aimed to provide evidence of the feasibility of conducting a randomized controlled trial to evaluate the efficacy of an e-cycling intervention to increase PA and improve health in individuals with T2DM. METHODS: A parallel-group two-arm randomized, waitlist-controlled pilot study was conducted. Individuals were randomized to either an e-bike intervention or standard care. The intervention incorporated two one-to-one e-bike skills training and behavioural counselling sessions delivered by a community-based cycling charity, followed by a 12-week e-bike loan with two further sessions with the instructors. Feasibility was assessed via measures related to recruitment, retention and intervention implementation. Post-intervention interviews with instructors and participants explored the acceptability of the study procedures and intervention. Clinical, physiological and behavioural outcomes were collected at baseline and post-intervention to evaluate the intervention's potential. RESULTS: Forty participants (M = 57) were randomized, of which 34 were recruited from primary care practices. Thirty-five participants were retained in the trial. The intervention was conducted with high fidelity (> 80% content delivered). E-bike training provided participants with the skills, knowledge and confidence needed to e-bike independently. Instructors reported being more confident delivering the skills training than behavioural counselling, despite acknowledging its importance. The study procedures were found to be acceptable to participants. Between-group differences in change during the intervention were indicative of the interventions potential for improving glucose control, health-related quality of life and cardiorespiratory fitness. Increases in overall device measured moderate-to-vigorous PA behaviour following the intervention were found, and there was evidence that this population self-selected to e-cycle at a moderate intensity. CONCLUSIONS: The study's recruitment, retention, acceptability and potential efficacy support the development of a definitive trial subject to identified refinements. TRIAL REGISTRATION: ISRCTN, ISRCTN67421464 . Registered 17/12/2018.
16Physical activity when riding an electric assisted bicycle.PubMed
Sveinung Berntsen, Lena Malnes, Aleksander Langåker, et al.
Int J Behav Nutr Phys Act. 2017 Apr 26;14(1):55. doi: 10.1186/s12966-017-0513-z.
BACKGROUND: The objectives of the present study were to compare time spent cycling, exercise intensity, and time spent in moderate- (MPA) and vigorous intensity physical activity (VPA) when cycling on an E-bike and a conventional bicycle on two "cycling-to-work" routes with differences in topography, defined as a hilly and a flat route. METHODS: Eight adults (23-54 years, two women) cycled outdoors on a conventional bicycle and an E-bike, on a flat (8.2 km) and a hilly (7.1 km) route, resulting in 32 journeys. Duration, elevation, and oxygen consumption were recorded using a portable oxygen analyser with GPS. A maximal cardiorespiratory fitness test was performed on a cycle ergometer. Resting metabolic rate was obtained by indirect calorimetry with a canopy hood. RESULTS: The participants spent less time (median (IQR)) cycling on the E-bike compared with the conventional bicycle, on both the hilly (18.8 (4.9) vs. 26.3 (6.4) minutes) and the flat (20.0 (2.9) vs. 23.8 (1.8) minutes) routes. Lower exercise intensity was observed with the E-bike compared with the conventional bicycle, both on the hilly (50 (18) vs. 60 (22) % of maximal oxygen uptake) and the flat (52 (19) vs. 55 (12) % of maximal oxygen uptake) routes. In both cycling modes, most time was spent in MVPA (92-99%). However, fewer minutes were spent in MVPA with the E-bike than the conventional bicycle, for both the hilly (26% lower) and the flat (17% lower) routes. Cycling on the E-bike also resulted in 35 and 15% fewer minutes in vigorous intensity, respectively on the hilly and flat routes. CONCLUSION: Cycling on the E-bike resulted in lower trip duration and exercise intensity, compared with the conventional bicycle. However, most of the time was spent in MVPA. This suggests that changing the commuting mode from car to E-bike will significantly increase levels of physical activity while commuting.
17From cars to bikes - the feasibility and effect of using e-bikes, longtail bikes and traditional bikes for transportation among parents of children attending kindergarten: design of a randomized cross-over trial.PubMed
Helga Birgit Bjørnarå, Sveinung Berntsen, Saskia J Te Velde, et al.
BMC Public Health. 2017 Dec 28;17(1):981. doi: 10.1186/s12889-017-4995-z.
BACKGROUND: The present study aims to increase bicycling and level of physical activity (PA), and thereby promote health in parents of toddlers, by giving access to different bicycle types. There is a need for greater understanding of e-bikes and their role in the transportation network, and further effects on PA levels and health. Moreover, longtail bikes could meet certain practical needs not fulfilled by e-bikes or traditional bikes, hence increased knowledge regarding their feasibility should be obtained. No previous studies have investigated whether providing an e-bike or a longtail bike over an extended period in a sample of parents of toddlers influence objectively assessed amount of bicycling and total PA level, transportation habits, cardiorespiratory fitness, body composition and blood pressure. METHODS: A randomized cross-over trial will be performed, entailing that participants in the intervention group (n = 18) complete the following intervention arms in random order: (i) three months access to an e-bicycle with trailer for child transportation (n = 6), (ii) three months access to a longtail bicycle (n = 6), and (iii) three months access to a regular bicycle with trailer (n = 6), in total nine months. Also, a control group (n = 18) maintaining usual transportation and PA habits will be included. A convenience sample consisting of 36 parents of toddlers residing in Kristiansand municipality, Southern Norway, will be recruited. Total amount of bicycling (distance and time), total level of PA, and transportation habits will be measured at baseline and in connection to each intervention arm. Cardiorespiratory fitness, body composition and blood pressure will be measured at baseline and post-intervention. Main outcome will be bicycling distance and time spent cycling. DISCUSSION: New knowledge relevant for the timely issues of public health and environmental sustainability will be provided among parents of toddlers, representing a target group of greatest importance. There is a call for research on the influence of e-bikes and longtail bikes on travel behavior and PA levels, and whether voluntary cycling could improve health. If the present study reveals promising results, it should be replicated in larger and more representative samples. Eventually, inclusion in national public health policies should be considered. TRIAL REGISTRATION: ID NCT03131518 , made public 26.04.2017.
18Disparate Mechanisms of Fatigability in Response to Prolonged Running versus Cycling of Matched Intensity and Duration.PubMed
Callum G Brownstein, Mélanie Metra, Frederic Sabater Pastor, et al.
Med Sci Sports Exerc. 2022 May 1;54(5):872-882. doi: 10.1249/MSS.0000000000002863. Epub 2022 Jan 24.
INTRODUCTION: Running and cycling represent two of the most common forms of endurance exercise. However, a direct comparison of the neuromuscular consequences of these two modalities after prolonged exercise has never been made. The aim of this study was to compare the alterations in neuromuscular function induced by matched-intensity and duration cycling and running exercise. METHODS: During separate visits, 17 endurance-trained male participants performed 3 h of cycling and running at 105% of the gas exchange threshold. Neuromuscular assessments were taken are preexercise, midexercise, and postexercise, including knee extensor maximal voluntary contractions (MVC), voluntary activation (VA), high- and low-frequency doublets (Db100 and Db10, respectively), potentiated twitches (Qtw,pot), motor evoked potentials (MEP), and thoracic motor evoked potentials (TMEP). RESULTS: After exercise, MVC was similarly reduced by ~25% after both running and cycling. However, reductions in VA were greater after running (-16% ± 10%) than cycling (-10% ± 5%; P < 0.05). Similarly, reductions in TMEP were greater after running (-78% ± 24%) than cycling (-15% ± 60%; P = 0.01). In contrast, reductions in Db100 (running vs cycling, -6% ± 21% vs -13% ± 6%) and Db10:100 (running vs cycling, -6% ± 16% vs -19% ± 13%) were greater for cycling than running (P ≤ 0.04). CONCLUSIONS: Despite similar decrements in the knee extensor MVC after running and cycling, the mechanisms responsible for force loss differed. Running-based endurance exercise is associated with greater impairments in nervous system function, particularly at the spinal level, whereas cycling-based exercise elicits greater impairments in contractile function. Differences in the mechanical and metabolic demands imposed on the quadriceps could explain the disparate mechanisms of neuromuscular impairment after these two exercise modalities.
19Etiology of Neuromuscular Fatigue After Repeated Sprints Depends on Exercise Modality.PubMed
Katja Tomazin, Jean-Benoit Morin, Guillaume Y Millet
Int J Sports Physiol Perform. 2017 Aug;12(7):878-885. doi: 10.1123/ijspp.2016-0200. Epub 2016 Dec 5.
PURPOSE: To compare neuromuscular fatigue induced by repeated-sprint running vs cycling. METHODS: Eleven active male participants performed 2 repeated-maximal-sprint protocols (5×6 s, 24-s rest periods, 4 sets, 3 min between sets), 1 in running (treadmill) and 1 in cycling (cycle ergometer). Neuromuscular function, evaluated before (PRE); 30 s after the first (S1), the second (S2), and the last set (LAST); and 5 min after the last set (POST5) determined the knee-extensor maximal voluntary torque (MVC); voluntary activation (VA); single-twitch (Tw), high- (Db100), and low- (Db10) frequency torque; and maximal muscle compound action potential (M-wave) amplitude and duration of vastus lateralis. RESULTS: Peak power output decreased from 14.6 ± 2.2 to 12.4 ± 2.5 W/kg in cycling (P < .01) and from 21.4 ± 2.6 to 15.2 ± 2.6 W/kg in running (P < .001). MVC declined significantly from S1 in running but only from LAST in cycling. VA decreased after S2 (~-7%, P < .05) and LAST (~-9%, P < .01) set in repeated-sprint running and did not change in cycling. Tw, Db100, and Db10/Db100 decreased to a similar extent in both protocols (all P < .001 post-LAST). Both protocols induced a similar level of peripheral fatigue (ie, low-frequency peripheral fatigue, no changes in M-wave characteristics), while underlying mechanisms probably differed. Central fatigue was found only after running. CONCLUSION: Findings about neuromuscular fatigue resulting from RS cycling cannot be transferred to RS running.
20Effect of Seat Tube Angle and Exercise Intensity on Muscle Activity Patterns in Cyclists.PubMed
Will Duggan, Bernard Donne, Neil Fleming
Int J Exerc Sci. 2017 Dec 1;10(8):1145-1156. doi: 10.70252/GCPA3105. eCollection 2017.
Previous studies have reported improved efficiency at steeper seat tube angle (STA) during ergometer cycling; however, neuromuscular mechanisms have yet to be fully determined. The current study investigated effects of STA on lower limb EMG activity at varying exercise intensities. Cyclists (n=11) were tested at 2 workloads; 160W and an individualised workload (IWL) equivalent to lactate threshold (T) minus 10%δ (derived from maximal incremental data), using 3 STA (70, 75 and 80°). Electromyographic data from (VM), (RF), (VL) and (BF) were assessed. The timing and magnitude of activation were quantified and analysed using a two-way ANOVA. STA had significant ( < 0.05) effects on timing of onset and offset of VM, timing of offset of VL, and angle at peak for RF all occurring later at 80 vs. 70° STA at IWL. In RF, increased activity occurred during the first 108° of the crank cycle at 80 vs. 70° at IWL ( < 0.01). As most of the power in the pedal stroke is generated during the mid-section of the down-stroke, movement of the activation range of knee extensors into the predominantly power phase of the pedal stroke would potentially account for increased efficiency and decreased cardio-respiratory costs. Greater activity of bi-articular RF, in the first 108º of the crank cycle at IWL (80 vs. 70º) may more closely resemble the pelvic stabilising activity of RF in running biomechanics; and potentially explain the more effective transition from cycling to running reported in triathletes using steeper STA.
21Efficacy of Interval Training in Improving Body Composition and Adiposity in Apparently Healthy Adults: An Umbrella Review with Meta-Analysis.PubMed
Eric Tsz-Chun Poon, Hong-Yat Li, Jonathan Peter Little, et al.
Sports Med. 2024 Nov;54(11):2817-2840. doi: 10.1007/s40279-024-02070-9. Epub 2024 Jul 14.
BACKGROUND: Although the efficacy of interval training for improving body composition has been summarized in an increasing number of systematic reviews in recent years, discrepancies in review findings and conclusions have been observed. OBJECTIVE: This study aims to synthesize the available evidence on the efficacy of interval training compared with moderate-intensity continuous training (MICT) and nonexercise control (CON) in reducing body adiposity in apparently healthy adults. METHODS: An umbrella review with meta-analysis was performed. A systematic search was conducted in seven databases (MEDLINE, EMBASE, Cochrane Database, CINAHL, Scopus, SPORTDiscus, and Web of Science) up to October 2023. Systematic reviews with meta-analyses of randomized controlled trials (RCTs) comparing interval training and MICT/CON were included. Literature selection, data extraction, and methodological quality assessment (AMSTAR-2) were conducted independently by two reviewers. Meta-analyses were performed using a random-effects model. Subgroup analyses were conducted based on the type of interval training [high-intensity interval training (HIIT) and sprint interval training (SIT)], intervention duration, body mass index, exercise modality, and volume of HIIT protocols. RESULTS: Sixteen systematic reviews, including 79 RCTs and 2474 unique participants, met the inclusion criteria. Most systematic reviews had a critically low (n = 6) or low (n = 6) AMSTAR-2 score. Interval training demonstrated significantly greater reductions in total body fat percent (BF%) compared with MICT [weighted mean difference (WMD) of - 0.77%; 95% confidence interval (CI) - 1.12 to - 0.32%] and CON (WMD of - 1.50%; 95% CI - 2.40 to - 0.58%). Significant reductions in fat mass, visceral adipose tissue, subcutaneous abdominal fat, and android abdominal fat were also observed following interval training compared to CON. Subgroup analyses indicated that both HIIT and SIT resulted in superior BF% loss than MICT. These benefits appeared to be more prominent in individuals with overweight/obesity and longer duration interventions (≥ 12 weeks), as well as in protocols using cycling as a modality and low-volume HIIT (i.e., < 15 min of high-intensity exercise per session). CONCLUSIONS: This novel umbrella review with large-scale meta-analysis provides an updated synthesis of evidence with implications for physical activity guideline recommendations. The findings support interval training as a viable exercise strategy for reducing adiposity in the general population.
22Effects of cycling on the morphology and spinal posture in professional and recreational cyclists: a systematic review.PubMed
José A Antequera-Vique, José M Oliva-Lozano, José M Muyor
Sports Biomech. 2023 Apr;22(4):567-596. doi: 10.1080/14763141.2022.2058990. Epub 2022 Apr 19.
The aim was to know if cycling affects spinal morphology in postures off the bicycle, such as adapting the spinal curvatures on the bicycle depending on the handlebar type and position on the handlebars. A systematic review was conducted following the PRISMA guidelines. The studies selected met the following criteria: a) the study design was cross-sectional or longitudinal (experimental or cohorts); b) the study evaluated the sagittal morphology of the spine on the bicycle; c) the study included healthy and trained participants without injuries or cyclists reporting low back pain. Fifteen studies reported that a greater pelvic tilt was observed that when the handlebar was in a lower position. Sixteen studies found that lumbar kyphosis was greater when the handlebar grip was lower and farther from the saddle. Twelve studies reported that a tendency towards greater thoracic flexion as the time spent pedalling on the bicycle increased. In conclusion, the practice of cycling produces adaptations in the morphology of the spine of the cyclist compared to non-cyclists, such as an increase in pelvic tilt and a greater capacity for lumbar flexion in trunk flexion positions, and a greater thoracic kyphosis in the standing position.
23Effects of Cycling on Spine: A Case-Control Study Using a 3D Scanning Method.PubMed
Antonino Patti, Valerio Giustino, Giuseppe Messina, et al.
Sports (Basel). 2023 Nov 15;11(11):227. doi: 10.3390/sports11110227.
BACKGROUND: Few studies have investigated the effects of adopting a specific and prolonged posture on cyclists. This study aimed to evaluate the upright spine in a sample of recreational cyclists and compare it with a sample of non-cyclists, though still athletes, through a 3D scanning method. METHODS: Forty-eight participants were enrolled in this observational study. The sample consisted of 25 cyclists for the cycling group and 23 non-cyclist athletes for the control group. The Spine3D device (Sensor Medica, Guidonia Montecelio, Rome, Italy) was used to evaluate the spine of the participants in both groups. RESULTS: The results showed significantly greater spine inclination in the cycling group compared to the control group ( < 0.01). Furthermore, there was a significant decrease in lumbar lordosis in the cycling group compared to the control group ( < 0.01). CONCLUSIONS: This case-control study raises the possibility that the onset of lower back pain in cyclists may be due to a reduction in lumbar lordosis. Furthermore, this study demonstrated that the Spine3D device can be used in sports to monitor the spine of athletes to prevent and reduce musculoskeletal deficits.
24Adaptation of the lumbar spine to different positions in bicycle racing.PubMed
J Usabiaga, R Crespo, I Iza, et al.
Spine (Phila Pa 1976). 1997 Sep 1;22(17):1965-9. doi: 10.1097/00007632-199709010-00004.
STUDY DESIGN: A radiologic and electromyographic study was done of the adaptation of the lumbar spine to high-performance cycling. OBJECTIVES: To evaluate changes in the lumbar spine produced by different cycling positions on different types of bicycles used during competition. METHODS: Three professional cyclists were observed to evaluate changes in the lumbar spine. Radiographs were obtained of the different positions adopted by the cyclists during competition, and changes in the angles of the lumbar spine were measured. An electromyographic study was done of the abdominal, lumbar, and thoracic paravertebral muscles. RESULTS: The cyclists' positions involved a change from discal lordosis to kyphosis. To obtain a more aerodynamic position, the cyclists flexed the hip and made the pelvis horizontal without changing disc angles. The contraction of paravertebral lumbar muscles was proportional to pedalling intensity and decreased in more aerodynamic positions. The tone of the paravertebral thoracic muscles depended on the extent of cervical hyperextension. Abdominal muscles remained relaxed in all bicycle positions and with all pedalling intensities. CONCLUSIONS: The changes observed could modify the normal biomechanics of the lumbar spine, but the overall mechanical load on the spine is reduced by shifting weight onto the upper limbs. The imbalance that occurs between the activity of flexor and extensor muscles could cause lumbar pain in persons without proper physical preparation.
25Evaluation of Dynamic Spinal Morphology and Core Muscle Activation in Cyclists-A Comparison between Standing Posture and on the Bicycle.PubMed
José M Muyor, José A Antequera-Vique, José M Oliva-Lozano, et al.
Sensors (Basel). 2022 Dec 1;22(23):9346. doi: 10.3390/s22239346.
(1) Background: Cycling is characterized by a sustained sitting posture on the bicycle, where physiologic spinal curvatures are modified from standing to cycling. Therefore, the main objective was to evaluate and compare the morphology of the spine and the core muscle activity in standing posture and cycling at low intensity. (2) Methods: Twelve competitive cyclists participated in the study. Spinal morphology was evaluated using an infrared-camera system. Muscle activation was recorded using a surface electromyography device. (3) Conclusions: The lumbar spine changes its morphology from lordosis in standing to kyphosis (lumbar flexion) when pedaling on the bicycle. The sacral tilt significantly increases its anterior tilt when cycling compared to when standing. The spinal morphology and sacral tilt are dynamic depending on the pedal's position during the pedal stroke quadrants. The infraspinatus, latissimus dorsi, external oblique, and pectoralis major showed significantly higher activation pedaling than when standing, although with very low values.
26Upper limb and trunk muscle activity patterns during seated and standing cycling.PubMed
Nicolas A Turpin, Antony Costes, Pierre Moretto, et al.
J Sports Sci. 2017 Mar;35(6):557-564. doi: 10.1080/02640414.2016.1179777. Epub 2016 May 2.
The objective of this study is to clarify the functional roles of upper limb muscles during standing and seated cycling when power output increases. We investigated the activity of seven upper limb and trunk muscles using surface electromyography (EMG). Power outputs ranged from ~100-700 W with a pedalling frequency of 90 revolution per minute. Three-dimensional handle and pedal forces were simultaneously recorded. Using non-negative matrix factorisation, we extracted muscle synergies and we analysed the integrated EMG and EMG temporal patterns. Most of the muscles showed tonic activity that became more phasic as power output increased. Three muscle synergies were identified, associated with (i) torso stabilisation, (ii) compensation/generation of trunk accelerations and (iii) upper body weight support. Synergies were similar for seated and standing positions (Pearson's r > 0.7), but synergy #2 (biceps brachii, deltoidus and brachioradialis) was shifted forward during the cycle (~7% of cycle). The activity levels of synergy #1 (latissimus dorsi and erector spinae) and synergy #2 increased markedly above ~500 W (i.e., ~+40-70% and +130-190%) and during periods corresponding to ipsi- and contralateral downstrokes, respectively. Our study results suggest that the upper limb and trunk muscles may play important roles in cycling when high power outputs are required.
27Effect of incremental intensities on the spinal morphology and core muscle activation in competitive cyclists.PubMed
José M Muyor, José A Antequera-Vique, José M Oliva-Lozano, et al.
Sports Biomech. 2023 Apr;22(4):597-620. doi: 10.1080/14763141.2022.2097945. Epub 2022 Jul 14.
Cycling is a sport where cyclists predominantly adopt a sitting posture, with the trunk tilted forward. This posture requires a high volume of training and duration in several intensities of effort. This study aims to: 1) evaluate the behaviour of the thoracic and lumbar spine flexion and sacral inclination in the sagittal plane, the thoracic and lumbar spine flexion in the frontal plane, and the trunk torsion in the transverse plane; 2) compare the activation of the core muscles as the intensity of effort increases during an incremental test in cycling, and 3) identify which core muscle has a greater activation in each intensity zone. The spinal posture and the activation of the eight core muscles were evaluated in twelve competitive cyclists during incremental cycling intensities. Thoracic and lumbar spine flexion and sacral inclination statistically increased as the intensity of effort increased (Start < VT1 < VT2 < VO2max). A significant increase in muscle activation was observed in all core muscles evaluated as the intensity increased. The rectus abdominis showed statistically significant greater muscle activation than the other core muscles evaluated. In conclusion, as the intensity of effort in cycling increases, cyclists significantly increase the thoracic and lumbar spine flexion, the sacral inclination in the sagittal plane, the thoracic and lumbar spine flexion in the frontal plane, trunk rotation in the transverse plane, as well as the activation of the core muscles.
28Spinal posture of thoracic and lumbar spine and pelvic tilt in highly trained cyclists.PubMed
José M Muyor, Pedro A López-Miñarro, Fernando Alacid
J Sports Sci Med. 2011 Jun 1;10(2):355-61. eCollection 2011.
The aim of this study was to evaluate sagittal thoracic and lumbar spinal curvatures and pelvic tilt in elite and master cyclists when standing on the floor, and sitting on a bicycle at three different handlebar-hand positions. A total of 60 elite male cyclists (mean age: 22.95 ± 3.38 years) and 60 master male cyclists (mean age: 34.27 ± 3.05 years) were evaluated. The Spinal Mouse system was used to measure sagittal thoracic and lumbar curvature in standing on the floor and sitting positions on the bicycle at three different handlebar-hand positions (high, medium, and low). The mean values for thoracic and lumbar curvatures and pelvic tilt in the standing position on the floor were 48.17 ± 8.05°, -27.32 ± 7.23°, and 13.65 ± 5.54°, respectively, for elite cyclists and 47.02 ± 9.24°, -25.30 ± 6.29°, and 11.25 ± 5.17° for master cyclists. A high frequency of thoracic hyperkyphosis in the standing position was observed (58.3% in elite cyclists and 53.3% in master cyclists), whereas predominately neutral values were found in the lumbar spine (88.3% and 76.7% in elite and master cyclists, respectively). When sitting on the bicycle, the thoracic curve was at a lower angle in the three handlebar-hand positions with respect to the standing position on the floor in both groups (p < 0.01). The lumbar curve adopted a kyphotic posture. In conclusion, cyclists present a high percentage of thoracic hyperkyphotic postures in standing positions on the floor. However, thoracic hyperkyphosis is not directly related to positions adopted on the bicycle. Key pointsThis study evaluated thoracic and lumbar spinal curvatures and pelvic tilt in elite and master cyclists while standing and sitting on the bicycle.Elite and master cyclists showed a high frequency of thoracic hyperkyphosis and neutral lumbar lordosis in standing.Cyclists adopted a significantly lower thoracic kyphosis on the bicycle at the three handlebar positions analysed (upper, middle and lower handlebars) than in standing posture. The lumbar spine showed a kyphotic posture.The high percentage of standing thoracic hyperkyphosis in both groups of cyclists may be related to factors other than the specific posture adopted while cycling. Lumbar kyphosis on the bicycle may not affect the sagittal configuration of the lumbar spine in standing.
29Upper Body Posture and Muscle Activation in Recreational Cyclists: Immediate Effects of Variable Cycling Setups.PubMed
Andreas Brand, Thomas Sepp, Isabella Klöpfer-Krämer, et al.
Res Q Exerc Sport. 2020 Jun;91(2):298-308. doi: 10.1080/02701367.2019.1665620. Epub 2019 Nov 13.
: Discomfort during cycling can be counteracted by adjusting the seat position. However, the influence of changes in cycling position regarding quantitative biomechanical adaptions of the upper body in recreational cyclists is unclear. This study aims to investigate the effects of saddle position and reach distance on upper body kinematics and muscle activation. : Twelve recreational cyclists were investigated in four different sitting positions on an adjustable cycle trainer. Trunk, pelvis, shoulder, elbow and spinal kinematics as well as lower back and elbow extensor activity were analyzed for combinations of normal and shortened reach distance including horizontal and 10° downward inclined saddle positions. : An inclined saddle increased activation of elbow extensors by almost 23 ± 8% ( < .01) while a shortened reach distance resulted in a more posterior pelvic tilt of up to 18 ± 2% ( < .01) and less trunk forward lean of 10 ± 9% ( < .01). Shoulder flexion reduced by up to 23 ± 16% ( < .05) while elbow flexion increased by 15 ± 22% ( < .05) with a shortened reach distance. No differences between configurations were found for spinal kinematics and lower back muscle activity. : Changing the reach distance showed considerable biomechanical effects on upper body kinematics of the pelvis and trunk rather than on the spine or on lower back muscle activity. For reach distance, most compensation of postural changes of the upper body occurred by changes of shoulder and elbow angles while elbow extensor activation was only altered by saddle downward inclination.
30Respiratory Mechanical and Cardiorespiratory Consequences of Cycling with Aerobars.PubMed
Jesse M Charlton, Andrew H Ramsook, Reid A Mitchell, et al.
Med Sci Sports Exerc. 2017 Dec;49(12):2578-2584. doi: 10.1249/MSS.0000000000001393.
PURPOSE: Aerobars place a cyclist in a position where the trunk is flexed forward and the elbows are close to the midline of the body. This position is known to improve cycling aerodynamics and time trial race performance compared with upright cycling positions. However, the aggressive nature of this position may have important cardiorespiratory and metabolic consequences. The purpose of this investigation was to examine the respiratory mechanical, ventilatory, metabolic, and sensory consequences of cycling while using aerobars during laboratory-based cycling. METHODS: Eleven endurance-trained male cyclists (age, 26 ± 9 yr; V˙O2peak, 55 ± 5 mL·kg·min) were recruited. Visit 1 consisted of an incremental cycling test to determine peak power output. Visit 2 consisted of 6-min bouts of constant load cycling at 70% of peak incremental power output in the aerobar position, drop position, and upright position while grasping the brake hoods. Metabolic and ventilatory responses were measured using a commercially available metabolic cart, and respiratory pressures were measured using an esophageal catheter. RESULTS: Cycling in the aerobar position significantly increased the work of breathing (Wb), power of breathing (Pb), minute ventilation, ventilatory equivalent for oxygen and carbon dioxide, and transdiaphragmatic pressure compared with the upright position. Increases in the Wb and Pb in the aerobars relative to the upright position were strongly correlated with the degree of thoracic restriction, measured as the shoulder-to-aerobar width ratio (Wb: r = 0.80, P = 0.01; Pb: r = 0.69, P = 0.04). CONCLUSIONS: Aerobars significantly increase the mechanical cost of breathing and leads to greater ventilatory inefficiency compared with upright cycling. Future work is needed to optimize aerobar width to minimize the respiratory mechanical consequences while optimizing aerodynamics.
31Pain and body position on the bicycle in competitive and recreational road cyclists: A retrospective study.PubMed
Rodrigo R Bini, Jayden R Hunter
Sports Biomech. 2023 Apr;22(4):522-535. doi: 10.1080/14763141.2021.1942967. Epub 2021 Jun 18.
This study compared the presence of pain in recreational and competitive road cyclists and body position on the bicycle between cyclists with and without pain. Seventy-one cyclists completed a survey reporting existing cycling-related sites of pain and comfort. Static sagittal and frontal plane images were taken to analyse body position on the bicycle. Participants were separated into recreational and competitive road cycling groups, and further into cyclists reporting pain in the upper body, low back, buttocks/hips and knees for comparison with cyclists without pain. A logistic regression model investigated possible predictors of pain whilst cycling. Pain was present in 67% of recreational and 70% of competitive cyclists whilst comfort was reported by 81% of recreational and 75% of competitive cyclists. Trivial to moderate non-significant differences were observed for body position on the bicycle between cyclists with and without pain, and between cyclists with and without pain in the upper body, low back, buttocks/hips and knees. The predictive logistic model was not significant (p = 0.07) with a model fit predicted by McFadden R of 0.07. Given most cyclists reported both pain and comfort, comfort is probably not a good predictor of overuse injury risk.
32The club-level road cyclist: injury, pain, and performance.PubMed
Miriah Dahlquist, Marie-Christine Leisz, Marsha Finkelstein
Clin J Sport Med. 2015 Mar;25(2):88-94. doi: 10.1097/JSM.0000000000000111.
OBJECTIVE: The aims of this study were to (1) examine riding habits of injured cyclists, (2) identify factors related to seeking medical treatment, (3) investigate performance of recreational road cyclists compared with established norms regarding strength and flexibility measures, and (4) propose cycling-specific injury risk factors. DESIGN: Observational and prospective study. SETTING: Cycling store and bicycle distribution company. PARTICIPANTS: Sixty-three experienced road cyclists. ASSESSMENT OF RISK FACTORS: Initial data collection included a questionnaire. A 2-week training diary and 8 weekly follow-up injury questionnaires were also collected. MAIN OUTCOME MEASURES: Training habits and injury history, bike fit, flexibility, and isometric, dynamic, and plyometric strength measures. RESULTS: Participants were likely to have an injury at baseline, and chronic pain was common. Cyclists trained for an equal quantity of time irrespective of experiencing pain. Injury severity in terms of pain level and participant age were factors in seeking medical care. Our participants performed poorly on our testing protocol compared with available norms. Flexibility, strength, and bike fit measures did not predict injury. Previous injury predicted prospective injury. The knee and lumbar region were most frequently injured. CONCLUSIONS: Cycling is a sport in which injury risk and prevention need to be further studied. Cyclists are frequently injured but continue to participate in cycling at volumes equal to their healthy peers. CLINICAL RELEVANCE: This study outlines a clinically reproducible cyclist assessment and discusses behaviors common to the cycling patient.
33Risk Factors for Low Back Pain: A Population-Based Longitudinal Study.PubMed
Rahman Shiri, Kobra Falah-Hassani, Markku Heliövaara, et al.
Arthritis Care Res (Hoboken). 2019 Feb;71(2):290-299. doi: 10.1002/acr.23710.
OBJECTIVE: To identify risk factors for low back pain (LBP) and lumbar radicular pain and to assess whether obesity and exposure to workload factors modify the effect of leisure-time physical activity on LBP and lumbar radicular pain. METHODS: The population of this 11-year longitudinal study consists of a nationally representative sample of Finns ages ≥30 years (n = 3,505). The outcomes of the study were LBP and lumbar radicular pain for >7 days or for >30 days in the past 12 months at follow-up. RESULTS: LBP and lumbar radicular pain were more common in women than in men. LBP slightly declined with increasing age, while lumbar radicular pain increased with age. Abdominal obesity (defined by waist circumference) increased the risk of LBP (adjusted odds ratio [OR] 1.40 [95% confidence interval (95% CI) 1.16-1.68] for LBP >7 days and adjusted OR 1.41 [95% CI 1.13-1.76] for LBP >30 days) and general obesity (defined by body mass index) increased the risk of lumbar radicular pain (adjusted OR 1.44 [95% CI 1.12-1.85] for pain >7 days and adjusted OR 1.62 [95% CI 1.16-2.26] for pain >30 days). Smoking and strenuous physical work increased the risk of both LBP and lumbar radicular pain. Walking or cycling to work reduced the risk of LBP, particularly LBP for >30 days (adjusted OR 0.75 [95% CI 0.59-0.95]), with the largest reductions among nonabdominally obese individuals and among those not exposed to physical workload factors. Using vibrating tools increased the risk of lumbar radicular pain. CONCLUSION: Lifestyle and physical workload factors increase the risk of LBP and lumbar radicular pain. Walking and cycling may have preventive potential for LBP.
34Enhancing function in older adults with chronic low back pain: a pilot study of endurance training.PubMed
Maura D Iversen, Anne H Fossel, Jeffrey N Katz
Arch Phys Med Rehabil. 2003 Sep;84(9):1324-31. doi: 10.1016/s0003-9993(03)00198-9.
OBJECTIVES: To assess the effectiveness of a bicycle endurance program in older adults with chronic low back pain (CLBP) and to identify correlates of exercise adherence. DESIGN: Prospective cohort. SETTING: Residential facilities and a tertiary care hospital. PARTICIPANTS: Adults with CLBP aged 55 years and older. Of 29 subjects who agreed to participate, 3 (10%) were deemed ineligible at baseline. Nineteen subjects (73%) were women, and the median age was 72 years. INTERVENTIONS: Subjects were assessed at baseline and at 6 and 12 weeks by using standardized questionnaires, physical examination, and endurance testing by a physical therapist. Subjects received a bicycle and instructions to exercise 3 times a week for 12 weeks at a set wattage. A trained rescarcher collected exercise data weekly. Main outcome measures The Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36), the lumbar spinal stenosis symptom severity and function scales, and kilocalories were used to assess change. RESULTS: At baseline, subjects were moderately impaired (mean SF-36 physical function score, 52.6). Eighteen (65%) completed the trial. At 12 weeks, physical functioning (SF-36) improved by 11%, mental health (Mental Health Inventory 5-Item Questionnaire) improved by 14%, and CLBP symptoms decreased by 8%. Reasons for withdrawing included illness, family issues, and bicycle-related discomfort. CONCLUSIONS: The bicycle program was safe and effective for improving functional status and well-being.
35Pilates exercise or stationary cycling for chronic nonspecific low back pain: does it matter? a randomized controlled trial with 6-month follow-up.PubMed
Paul W M Marshall, Suzanne Kennedy, Cristy Brooks, et al.
Spine (Phila Pa 1976). 2013 Jul 1;38(15):E952-9. doi: 10.1097/BRS.0b013e318297c1e5.
STUDY DESIGN: Randomized controlled trial. OBJECTIVE: This is the companion study to a previous publication that presented 8-week pain, disability, and trunk muscle motor control results. The objective of this study was to compare the effect of 8 weeks of specific trunk exercises and stationary cycling on outcomes measures of catastrophizing and fear-avoidance beliefs (FAB) in patients with chronic nonspecific low back pain, and provide 6-month outcome data for all self-report measures. SUMMARY OF BACKGROUND DATA: It is thought that any form of moderate-to-vigorous physical activity is sufficient to address catastrophizing and FAB, and concomitant levels of pain and disability. METHODS: Sixty-four patients with low back pain were randomly assigned to 8 weeks of specific trunk exercise group (SEG), or stationary cycling group (CEG). Self-rated pain, disability, catastrophizing and FAB scores were collected before, immediately after (8 wk), and 6 months after the training program. Clinically meaningful improvements were defined as greater than a 30% reduction from baseline in pain and disability scores. "Intention-to-treat" principles were used for missing data. Per-protocol analysis was performed on participants who attended at least two-thirds of the exercise sessions. RESULTS: At 8 weeks, disability was significantly lower in the SEG compared with the CEG (d = 0.62, P = 0.018). Pain was reduced from baseline in both the groups after training (P < 0.05), but was lower for the SEG (P < 0.05). FAB scores were reduced in the SEG at 8 weeks, and in the CEG at 6 months. No between-group differences in FAB scores were observed. Similar reductions in catastrophizing in each group were observed at each time point. At 6 months, the overall data pattern suggested no long-term difference between groups. Per-protocol analysis of clinically meaningful improvements suggests no between-group differences for how many patients are likely to report improvement. CONCLUSION: Inferential statistics suggest greater improvements at 8 weeks, but not 6 months, for the SEG. Inspection of clinically meaningful changes based on a minimum level of adherence suggests no between-group differences. If a patient with low back pain adheres to either specific trunk exercises or stationary cycling, it is reasonable to think that similar improvements will be achieved. LEVEL OF EVIDENCE: 2.
36Exercise capacity in non-specific chronic low back pain patients: a lean body mass-based Astrand bicycle test; reliability, validity and feasibility.PubMed
Audy P Hodselmans, Pieter U Dijkstra, Jan H B Geertzen, et al.
J Occup Rehabil. 2008 Sep;18(3):282-9. doi: 10.1007/s10926-008-9143-2. Epub 2008 Jul 15.
OBJECTIVE: Measurement of exercise capacity is essential in patients with non-specific chronic low back pain (CLBP). However, the conventional Astrand bicycle test is not feasible in patients with a very poor aerobic capacity. Therefore the Astrand bicycles test for non-specific CLBP patients based on lean body mass (LBM) was developed as an alternative. The aim of this study was to evaluate reliability and validity of the LBM-based Astrand test. SUBJECTS: Twenty patients with non-specific CLBP and 20 healthy subjects were included for the reliability evaluation, and 19 healthy subjects for the validity evaluation. METHOD: Patients and healthy subjects were assessed twice. Intra class correlation (ICC), repeatability coefficient (RC) and the limits of agreement (LOA) were calculated as a measure of test re-tests reliability. An ICC >or= 0.75 was considered acceptable. Validity was tested by calculating ICC between the LBM-based Astrand test and a maximal bicycle test. RESULTS: The LBM-based Astrand test shows good reliability, reflected by an ICC >or= 0.91 and 95% of the 20 patients could perform the test. However, differences with the estimated true value reflected by the RC and natural variation reflected by the LOA were substantial in patients. Validity was good, reflected by ICC >or= 0.88. CONCLUSION: The present study shows that the LBM-based Astrand test is a reliable, valid, and feasible method for patients with non-specific CLBP. However, a substantial amount of variation should be taken into account in patients when interpreting the test results clinically.
37Specific trunk and general exercise elicit similar changes in anticipatory postural adjustments in patients with chronic low back pain: a randomized controlled trial.PubMed
Cristy Brooks, Suzanne Kennedy, Paul W M Marshall
Spine (Phila Pa 1976). 2012 Dec 1;37(25):E1543-50. doi: 10.1097/BRS.0b013e31826feac0.
STUDY DESIGN: A randomized controlled trial. OBJECTIVE: To compare changes in self-rated disability, pain, and anticipatory postural adjustments between specific trunk exercise and general exercise in patients with chronic low back pain. SUMMARY OF BACKGROUND DATA: Chronic low back pain is associated with altered motor control of the trunk muscles. The best exercise to address altered motor control is unclear. METHODS: Sixty-four patients with chronic low back pain were randomly assigned to a specific trunk exercise group (SEG) that included skilled cognitive activation of the trunk muscles in addition to a number of other best practice exercises, whereas the general exercise group performed only seated cycling exercise. The training program lasted for 8 weeks. Self-rated disability and pain scores were collected before and after the training period. Electromyographic activity of various trunk muscles was recorded during performance of a rapid shoulder flexion task before and after training. Muscle onsets were calculated, and the latency time (in ms) between the onset of each trunk muscle and the anterior deltoid formed the basis of the motor control analysis. RESULTS: After training, disability was significantly lower in the SEG (d = 0.62, P = 0.018). Pain was reduced in both groups after training (P < 0.05), but was lower for the SEG (P < 0.05). Despite the general exercise group performing no specific trunk exercise, similar changes in trunk muscle onsets were observed in both groups after training. CONCLUSION: SEG elicited significant reductions in self-rated disability and pain, whereas similar between-group changes in trunk muscle onsets were observed. The motor control adaptation seems to reflect a strategy of improved coordination between the trunk muscles with the unilateral shoulder movement. Trunk muscle onsets during rapid limb movement do not seem to be a valid mechanism of action for specific trunk exercise rehabilitation programs.
38Lumbopelvic Core Stabilization Exercise and Pain Modulation Among Individuals with Chronic Nonspecific Low Back Pain.PubMed
Aatit Paungmali, Leonard H Joseph, Patraporn Sitilertpisan, et al.
Pain Pract. 2017 Nov;17(8):1008-1014. doi: 10.1111/papr.12552. Epub 2017 Feb 25.
BACKGROUND: Lumbopelvic stabilization training (LPST) may provide therapeutic benefits on pain modulation in chronic nonspecific low back pain conditions. This study aimed to examine the effects of LPST on pain threshold and pain intensity in comparison with the passive automated cycling intervention and control intervention among patients with chronic nonspecific low back pain. METHODS: A within-subject, repeated-measures, crossover randomized controlled design was conducted among 25 participants (7 males and 18 females) with chronic nonspecific low back pain. All the participants received 3 different types of experimental interventions, which included LPST, the passive automated cycling intervention, and the control intervention randomly, with 48 hours between the sessions. The pressure pain threshold (PPT), hot-cold pain threshold, and pain intensity were estimated before and after the interventions. RESULTS: Repeated-measures analysis of variance showed that LPST provided therapeutic effects as it improved the PPT beyond the placebo and control interventions (P < 0.01). The pain intensity under the LPST condition was significantly better than that under the passive automated cycling intervention and controlled intervention (P < 0.001). Heat pain threshold under the LPST condition also showed a significant trend of improvement beyond the control (P < 0.05), but no significant effects on cold pain threshold were evident. CONCLUSIONS: Lumbopelvic stabilization training may provide therapeutic effects by inducing pain modulation through an improvement in the pain threshold and reduction in pain intensity. LPST may be considered as part of the management programs for treatment of chronic low back pain.
39High-volume FES-cycling partially reverses bone loss in people with chronic spinal cord injury.PubMed
Angela Frotzler, Sylvie Coupaud, Claudio Perret, et al.
Bone. 2008 Jul;43(1):169-176. doi: 10.1016/j.bone.2008.03.004. Epub 2008 Mar 20.
Spinal cord injury (SCI) leads to severe bone loss in the paralysed limbs and to a resulting increased fracture risk thereof. Since long bone fractures can lead to comorbidities and a reduction in quality of life, it is important to improve bone strength in people with chronic SCI. In this prospective longitudinal cohort study, we investigated whether functional electrical stimulation (FES) induced high-volume cycle training can partially reverse the loss of bone substance in the legs after chronic complete SCI. Eleven participants with motor-sensory complete SCI (mean age 41.9+/-7.5 years; 11.0+/-7.1 years post injury) were recruited. After an initial phase of 14+/-7 weeks of FES muscle conditioning, participants performed on average 3.7+/-0.6 FES-cycling sessions per week, of 58+/-5 min each, over 12 months at each individual's highest power output. Bone and muscle parameters were investigated in the legs by means of peripheral quantitative computed tomography before the muscle conditioning (t1), and after six (t2) and 12 months (t3) of high-volume FES-cycle training. After 12 months of FES-cycling, trabecular and total bone mineral density (BMD) as well as total cross-sectional area in the distal femoral epiphysis increased significantly by 14.4+/-21.1%, 7.0+/-10.8% and 1.2+/-1.5%, respectively. Bone parameters in the femoral shaft showed small but significant decreases, with a reduction of 0.4+/-0.4% in cortical BMD, 1.8+/-3.0% in bone mineral content, and 1.5+/-2.1% in cortical thickness. These decreases mainly occurred between t1 and t2. No significant changes were found in any of the measured bone parameters in the tibia. Muscle CSA at the thigh increased significantly by 35.5+/-18.3%, while fat CSA at the shank decreased by 16.7+/-12.3%. Our results indicate that high-volume FES-cycle training leads to site-specific skeletal changes in the paralysed limbs, with an increase in bone parameters at the actively loaded distal femur but not the passively loaded tibia. Thus, we conclude that high-volume FES-induced cycle training has clinical relevance as it can partially reverse bone loss and thus may reduce fracture risk at this fracture prone site.
40Increases in bone mineral density after functional electrical stimulation cycling exercises in spinal cord injured patients.PubMed
Shih-Ching Chen, Chien-Hung Lai, Wing P Chan, et al.
Disabil Rehabil. 2005 Nov 30;27(22):1337-41. doi: 10.1080/09638280500164032.
PURPOSE: To assess the change in bone mineral density (BMD) after spinal cord injury (SCI) and to evaluate whether BMD loss can be reversed with the intervention of functional electric stimulation cycling exercises (FESCE). METHODS: Fifteen males with SCI were included. Fifteen able-bodied males were also tested to compare BMD. In the SCI group, the FESCE was performed for six months, and then was discontinued in the subsequent six months. BMD was performed before the FESCE, immediately after six months of the FESCE, and at the end of the subsequent six months. RESULTS: Before the FESCE, the BMD of the SCI subjects in every site, except the lumbar spine, was lower than that of the able-bodied subjects. After six months of FESCE, BMD of the distal femur (DF) and proximal tibia (PT) increased significantly, and BMD of the calcaneus (heel) showed a trend of increase. However, the BMD in the DF, PT, and heel decreased significantly after the subsequent six months without FESCE. The BMD of the femoral neck (FN) decreased progressively throughout the programme. CONCLUSIONS: Our study showed site-specific BMD changes after FESCE. The BMD loss in the DF and PT was partially reversed after six months of FESCE, but the effect faded once the exercise was discontinued.
41A Review of Functional Electrical Stimulation Treatment in Spinal Cord Injury.PubMed
Shiyu Luo, Haonan Xu, Yi Zuo, et al.
Neuromolecular Med. 2020 Dec;22(4):447-463. doi: 10.1007/s12017-019-08589-9. Epub 2020 Jan 8.
Functional electrical stimulation (FES) has been widely adopted to elicit muscle contraction in rehabilitation training after spinal cord injury (SCI). Conventional FES modalities include stimulations coupled with rowing, cycling, assisted walking and other derivatives. In this review, we studied thirteen clinical reports from the past 5 years and evaluated the effects of various FES aided rehabilitation plans on the functional recovery after SCI, highlighting upper and lower extremity strength, cardiopulmonary function, and balder control. We further explored potential mechanisms of FES using the Hebbian theory and lumbar locomotor central pattern generators. Overall, FES can be used to improve respiration, circulation, hand strength, mobility, and metabolism after SCI.
42Exercise prescription for persons with spinal cord injury: a review of physiological considerations and evidence-based guidelines.PubMed
Chelsea Pelletier
Appl Physiol Nutr Metab. 2023 Dec 1;48(12):882-895. doi: 10.1139/apnm-2023-0227. Epub 2023 Oct 10.
Persons with spinal cord injury (SCI) experience gains in fitness, physical and mental health from regular participation in exercise and physical activity. Due to changes in physiological function of the cardiovascular, nervous, and muscular systems, general population physical activity guidelines and traditional exercise prescription methods are not appropriate for the SCI population. Exercise guidelines specific to persons with SCI recommend progressive training beginning at 20 min of moderate to vigorous intensity aerobic exercise twice per week transitioning to 30 min three times per week, with strength training of the major muscle groups two times per week. These population-specific guidelines were designed considering the substantial barriers to physical activity for persons with SCI and can be used to frame an individual exercise prescription. Rating of perceived exertion (i.e., perceptually regulated exercise) is a practical way to indicate moderate to vigorous intensity exercise in community settings. Adapted exercise modes include arm cycle ergometry, hybrid arm-leg cycling, and recumbent elliptical equipment. Body weight-supported treadmill training and other rehabilitation modalities may improve some aspects of health and fitness for people with SCI if completed at sufficient intensity. Disability-specific community programs offer beneficial opportunities for persons with SCI to experience quality exercise opportunities but are not universally available.
43Effect of electrical stimulation-induced cycling on bone mineral density in spinal cord-injured patients.PubMed
P Eser, E D de Bruin, I Telley, et al.
Eur J Clin Invest. 2003 May;33(5):412-9. doi: 10.1046/j.1365-2362.2003.01156.x.
BACKGROUND: Bone atrophy in spinal cord-injured people (SCI) is, among other factors, caused by immobilization and is initiated shortly after the injury. The present study measured the effect of an functional electrical stimulation (FES)-cycling intervention on bone mineral density (BMD) of the tibia in recently injured SCI people. METHODS: As soon as possible after the injury (mean 4.5 weeks), para- and tetraplegic patients were recruited into an intervention and control group comparable with regard to gender, age, and lesion level. The intervention consisted of 30-min functional electrical stimulation-cycling three times a week for the duration of their primary rehabilitation (mean = 6 months). Computed tomography (CT) scans of the right tibia diaphysis were taken at the beginning and at the end of the intervention. Bone mineral density of cortical bone was calculated from the CT scans. RESULTS: A total of 38 subjects (19 in each group) were included in the study. Both groups showed a reduction in tibial cortical BMD of 0-10% of initial values within 3-10 months. The mean decrease in BMD was 0.3% (+/- 0.6) per month in the intervention group and 0.7% (+/- 0.8) in the control group. This difference did not reach statistical significance. Decrease of BMD was linearly correlated to initial BMD and age in the pooled data of both groups; subjects who had a high initial BMD and/or were older lost more bone. In neither group was bone loss associated with duration of immobilization nor lesion level. CONCLUSIONS: Functional electrical stimulation-cycling applied shortly after SCI did not significantly attenuate bone loss.
44Effects of functional electrical stimulation cycling exercise on bone mineral density loss in the early stages of spinal cord injury.PubMed
Chien-Hung Lai, Walter Hong-Shong Chang, Wing P Chan, et al.
J Rehabil Med. 2010 Feb;42(2):150-4. doi: 10.2340/16501977-0499.
OBJECTIVE: To determine whether bone mineral density loss after spinal cord injury can be attenuated by an early intervention with functional electrical stimulation cycling exercises (FESCE) and to ascertain whether the effect persists after FESCE is discontinued. DESIGN: A prospective study. SUBJECTS: Twenty-four individuals with spinal cord injury, 26-52 days after spinal cord injury, were divided into FESCE or control groups. METHODS: FESCE was applied in the initial 3 months and then suspended in the subsequent 3 months. Bone mineral density in the femoral neck and distal femur was measured using dual energy X-ray absorptiometry before training, immediately after the initial 3 months of training, and at the end of the subsequent 3 months. RESULTS: The bone mineral density decrease rate in the distal femur in the FESCE group was significantly less than that in the control group during the initial 3 months. However, there was no significant difference in the subsequent 3 months. CONCLUSION: FESCE in the early stages of spinal cord injury can partly attenuate bone mineral density loss in the distal femur. However, bone mineral density loss in the distal femur cannot be ameliorated completely by FESCE. In addition, the effect on the attenuation of bone loss in the distal femur faded once FESCE was discontinued.
45Effects of cycling and/or electrical stimulation on bone mineral density in children with spinal cord injury.PubMed
R T Lauer, B T Smith, M J Mulcahey, et al.
Spinal Cord. 2011 Aug;49(8):917-23. doi: 10.1038/sc.2011.19. Epub 2011 Mar 22.
STUDY DESIGN: Randomized clinical trial. OBJECTIVES: To determine the effect of cycling and/or electrical stimulation on hip and knee bone mineral density (BMD) in children with spinal cord injury (SCI). SETTING: Children's hospital specializing in pediatric SCI. METHODS: A total of 30 children, aged 5-13 years, with chronic SCI were randomized to one of three interventions: functional electrical stimulation cycling (FESC), passive cycling (PC), and non-cycling, electrically stimulated exercise (ES). Each group exercised for 1 h, three times per week for 6 months at home. The hip, distal femur and proximal tibia BMD were examined via dual-energy X-ray absorptiometry (DXA) pre- and post-intervention. RESULTS: In all, 28 children completed data collection. The FESC group exhibited increases in hip, distal femur and proximal tibia BMD of 32.4, 6.62 and 10.3%, respectively. The PC group exhibited increases at the hip (29.2%), but no change at the distal femur (1.5%) or proximal tibia (-1.0%). The ES group had no change at the hip (-0.24%) and distal femur (3.3%), but a loss at the proximal tibia (-7.06%). There were no differences between groups or within groups over time. Significant negative correlations were found between baseline BMD and the amount of BMD change. CONCLUSION: Although not achieving statistical significance, hip BMD changes observed were greater than the reported 0.9-10% gains after exercise for children with and without disability. Thus, cycling with and without electrical stimulation may be beneficial for skeletal health in pediatric SCI, but further research is needed with a larger sample size.
46Musculoskeletal Effects of 2 Functional Electrical Stimulation Cycling Paradigms Conducted at Different Cadences for People With Spinal Cord Injury: A Pilot Study.PubMed
Therese E Johnston, Ralph J Marino, Christina V Oleson, et al.
Arch Phys Med Rehabil. 2016 Sep;97(9):1413-1422. doi: 10.1016/j.apmr.2015.11.014. Epub 2015 Dec 17.
OBJECTIVE: To compare the musculoskeletal effects of low cadence cycling with functional electrical stimulation (FES) with high cadence FES cycling for people with spinal cord injury (SCI). DESIGN: Randomized pre-post design. SETTING: Outpatient rehabilitation clinic. PARTICIPANTS: Participants (N=17; 14 men, 3 women; age range, 22-67y) with C4-T6 motor complete chronic SCI were randomized to low cadence cycling (n=9) or high cadence cycling (n=8). INTERVENTIONS: Low cadence cycling at 20 revolutions per minute (RPM) and high cadence cycling at 50 RPM 3 times per week for 6 months. Cycling torque (resistance per pedal rotation) increased if targeted cycling cadence was maintained. MAIN OUTCOME MEASURES: Dual-energy x-ray absorptiometry was used to assess distal femur areal bone mineral density, magnetic resonance imaging was used to assess to assess trabecular bone microarchitecture and cortical bone macroarchitecture and thigh muscle volume, and biochemical markers were used to assess bone turnover. It was hypothesized that subjects using low cadence cycling would cycle with greater torque and therefore show greater musculoskeletal improvements than subjects using high cadence cycling. RESULTS: A total of 15 participants completed the study. Low cadence cycling obtained a maximal average torque of 2.9±2.8Nm, and high cadence cycling obtained a maximal average torque of 0.8±0.2Nm. Low cadence cycling showed greater decreases in bone-specific alkaline phosphatase, indicating less bone formation (15.5% decrease for low cadence cycling, 10.7% increase for high cadence cycling). N-telopeptide decreased 34% following low cadence cycling, indicating decreased resorption. Both groups increased muscle volume (low cadence cycling by 19%, high cadence cycling by 10%). Low cadence cycling resulted in a nonsignificant 7% increase in apparent trabecular number (P=.08) and 6% decrease in apparent trabecular separation (P=.08) in the distal femur, whereas high cadence cycling resulted in a nonsignificant (P>.3) 2% decrease and 3% increase, respectively. CONCLUSIONS: This study suggests that the greater torque achieved with low cadence cycling may result in improved bone health because of decreased bone turnover and improved trabecular bone microarchitecture. Longer-term outcome studies are warranted to identify the effect on fracture risk.
47A Comparison of FES and SCS for Neuroplastic Recovery After SCI: Historical Perspectives and Future Directions.PubMed
Lynsey D Duffell, Nicholas de Neufvillle Donaldson
Front Neurol. 2020 Jun 30;11:607. doi: 10.3389/fneur.2020.00607. eCollection 2020.
There is increasing evidence that neuroplastic changes can occur even years after spinal cord injury, leading to reduced disability and better health which should reduce the cost of healthcare. In motor-incomplete spinal cord injury, recovery of leg function may occur if repetitive training causes afferent input to the lumbar spinal cord. The afferent input may be due to activity-based therapy without electrical stimulation but we present evidence that it is faster with electrical stimulation. This may be spinal cord stimulation or peripheral nerve stimulation. Recovery is faster if the stimulation is phasic and that the patient is trying to use their legs during the training. All the published studies are small, so all conclusions are provisional, but it appears that patients with more disability (AIS A and B) may need to continue using stimulation and for them, an implanted stimulator is likely to be convenient. Patients with less disability (AIS C and D) may make useful recovery and improve their quality of life from a course of therapy. This might be locomotion therapy but we argue that cycling with electrical stimulation, which uses biofeedback to encourage descending drive, causes rapid recovery and might be used with little supervision at home, making it much less expensive. Such an electrical therapy followed by conventional physiotherapy might be affordable for the many people living with chronic SCI. To put this in perspective, we present some information about what treatments are funded in the UK and the US.
48Assessing sensorimotor excitability after spinal cord injury: a reflex testing method based on cycling with afferent stimulation.PubMed
Stefano Piazza, Diego Torricelli, Julio Gómez-Soriano, et al.
Med Biol Eng Comput. 2018 Aug;56(8):1425-1434. doi: 10.1007/s11517-018-1787-2. Epub 2018 Jan 17.
UNLABELLED: Several studies have examined spinal reflex modulation during leg cycling in healthy and spinal cord injury (SCI) subjects. However, the effect of cutaneous plantar afferent input on spinal excitability during leg cycling after SCI has not been characterised. The aim of the study was to test the feasibility of using controlled leg cycling in combination with plantar cutaneous electrical stimulation (ES) cycling to assess lower limb spinal sensorimotor excitability in subjects with motor complete or incomplete SCI. Spinal sensorimotor excitability was estimated by measuring cutaneomuscular-conditioned soleus H-reflex activity. Reflex excitability was tested before and after a 10-min ES cycling session in 13 non-injured subjects, 6 subjects with motor incomplete SCI (iSCI) who had moderately impaired gait function, 4 subjects with motor iSCI who had severely impaired gait function, and 5 subjects with motor complete SCI (cSCI). No modulation of soleus H-reflex with plantar cutaneous stimuli was observed after either iSCI or cSCI when compared to non-injured subjects. However, after ES cycling, reflex excitability significantly increased in subjects with iSCI and moderately impaired gait function. ES cycling facilitated spinal sensorimotor excitability only in subjects with motor iSCI with residual gait function. Increased spinal excitability induced with a combination of exercise and afferent stimulation could be adopted with diagnostic and prognostic purposes to reveal the activity-based neurorehabilitation profile of individual subjects with motor iSCI. TRIAL REGISTRATION: ISRCTN 26172500 ; retrospectively registered on 15 July 2016 Graphical abstract ᅟ.
49Exploiting cervicolumbar connections enhances short-term spinal cord plasticity induced by rhythmic movement.PubMed
Gregory E P Pearcey, E Paul Zehr
Exp Brain Res. 2019 Sep;237(9):2319-2329. doi: 10.1007/s00221-019-05598-9. Epub 2019 Jul 8.
Arm cycling causes suppression of soleus (SOL) Hoffmann (H-) reflex that outlasts the activity period. Arm cycling presumably activates propriospinal networks that modulate Ia presynaptic inhibition. Interlimb pathways are thought to relate to the control of quadrupedal locomotion, allowing for smooth, coordinated movement of the arms and legs. We examined whether the number of active limb pairs affects the amount and duration of activity-dependent plasticity of the SOL H-reflex. On separate days, 14 participants completed 4 randomly ordered 30 min experimental sessions: (1) quiet sitting (CTRL); (2) arm cycling (ARM); (3) leg cycling (LEG); and (4) arm and leg cycling (A&L) on an ergometer. SOL H-reflex and M-wave were evoked via electrical stimulation of the tibial nerve. M-wave and H-reflex recruitment curves were recorded, while the participants sat quietly prior to, 10 and 20 min into, immediately after, and at 2.5, 5, 7.5, 10, 15, 20, 25, and 30 min after each experimental session. Normalized maximal H-reflexes were unchanged in CTRL, but were suppressed by > 30% during the ARM, LEG, and A&L. H-reflex suppression outlasted activity duration for ARM (≤ 2.5 mins), LEG (≤ 5 mins), and A&L (≤ 30 mins). The duration of reflex suppression after A&L was greater than the algebraic summation of ARM and LEG. This non-linear summation suggests that using the arms and legs simultaneously-as in typical locomotor synergies-amplifies networks responsible for the short-term plasticity of lumbar spinal cord excitability. Enhanced activity of spinal networks may have important implications for the implementation of locomotor training for targeted rehabilitation.
50Can FES-Augmented Active Cycling Training Improve Locomotion in Post-Acute Elderly Stroke Patients?PubMed
Elisabetta Peri, Emilia Ambrosini, Alessandra Pedrocchi, et al.
Eur J Transl Myol. 2016 Jun 13;26(3):6063. doi: 10.4081/ejtm.2016.6063.
Recent studies advocated the use of active cycling coupled with functional electrical stimulation to induce neuroplasticity and enhance functional improvements in stroke adult patients. The aim of this work was to evaluate whether the benefits induced by such a treatment are superior to standard physiotherapy. A single-blinded randomized controlled trial has been performed on post-acute elderly stroke patients. Patients underwent FES-augmented cycling training combined with voluntary pedaling or standard physiotherapy. The intervention consisted of fifteen 30-minutes sessions carried out within 3 weeks. Patients were evaluated before and after training, through functional scales, gait analysis and a voluntary pedaling test. Results were compared with an age-matched healthy group. Sixteen patients completed the training. After treatment, a general improvement of all clinical scales was obtained for both groups. Only the mechanical efficiency highlighted a group effect in favor of the experimental group. Although a group effect was not found for any other cycling or gait parameters, the experimental group showed a higher percentage of change with respect to the control group (e.g. the gait velocity was improved of 35.4% and 25.4% respectively, and its variation over time was higher than minimal clinical difference for the experimental group only). This trend suggests that differences in terms of motor recovery between the two groups may be achieved increasing the training dose. In conclusion, this study, although preliminary, showed that FES-augmented active cycling training seems to be effective in improving cycling and walking ability in post-acute elderly stroke patients. A higher sample size is required to confirm results.
51Comparison of stimulation patterns for FES-cycling using measures of oxygen cost and stimulation cost.PubMed
K J Hunt, C Ferrario, S Grant, et al.
Med Eng Phys. 2006 Sep;28(7):710-8. doi: 10.1016/j.medengphy.2005.10.006. Epub 2005 Nov 18.
AIM: The energy efficiency of FES-cycling in spinal cord injured subjects is very much lower than that of normal cycling, and efficiency is dependent upon the parameters of muscle stimulation. We investigated measures which can be used to evaluate the effect on cycling performance of changes in stimulation parameters, and which might therefore be used to optimise them. We aimed to determine whether oxygen cost and stimulation cost measurements are sensitive enough to allow discrimination between the efficacy of different activation ranges for stimulation of each muscle group during constant-power cycling. METHODS: We employed a custom FES-cycling ergometer system, with accurate control of cadence and stimulated exercise workrate. Two sets of muscle activation angles ("stimulation patterns"), denoted "P1" and "P2", were applied repeatedly (eight times each) during constant-power cycling, in a repeated measures design with a single paraplegic subject. Pulmonary oxygen uptake was measured in real time and used to determine the oxygen cost of the exercise. A new measure of stimulation cost of the exercise is proposed, which represents the total rate of stimulation charge applied to the stimulated muscle groups during cycling. A number of energy-efficiency measures were also estimated. RESULTS: Average oxygen cost and stimulation cost of P1 were found to be significantly lower than those for P2 (paired t-test, p<0.05): oxygen costs were 0.56+/-0.03l min-1 and 0.61+/-0.04l min-1 (mean+/-S.D.), respectively; stimulation costs were 74.91+/-12.15 mC min-1 and 100.30+/-14.78 mC min-1 (mean+/-S.D.), respectively. Correspondingly, all efficiency estimates for P1 were greater than those for P2. CONCLUSION: Oxygen cost and stimulation cost measures both allow discrimination between the efficacy of different muscle activation patterns during constant-power FES-cycling. However, stimulation cost is more easily determined in real time, and responds more rapidly and with greatly improved signal-to-noise properties than the ventilatory oxygen uptake measurements required for estimation of oxygen cost. These measures may find utility in the adjustment of stimulation patterns for achievement of optimal cycling performance.
52Impotence and genital numbness in cyclists.PubMed
F Sommer, D König, C Graft, et al.
Int J Sports Med. 2001 Aug;22(6):410-3. doi: 10.1055/s-2001-16248.
Cyclists often complain of genital numbness and even of impotence. The purpose of this study was to determine if perineal compression during cycling causes changes in the penile blood supply, impotence and penile numbness. Forty healthy athletic men with a mean age of 30 +/- 5.3 years took part in the study. Transcutaneous penile oxygen pressure was obtained using a device consisting of a modified Clark pO2 electrode, attached to the glans of the penis. All men were measured in a standing position before, in a seated and standing position during and in a standing position after cycling. Additionally, a detailed interview was carried out with each man. The penile blood supply--which correlates with the transcutaneous PO2 at the glans-- decreased significantly in over 70% of the test subjects during cycling in a seated position. Cycling in a standing position did not show any alteration in the penile blood supply as compared to the values measured before exercising. Numbness of the genital region was reported by 61% of the cyclists. 19% of cyclists who had a weekly training distance of more than 400 km complained of erectile dysfunction. The results of the present study showed that there is a deficiency in penile perfusion due to perineal arterial compression. This could be a reason for penile numbness and impotence in long-distance cyclists. Therefore, we suggest restricting the training distance, and taking sufficient pauses during the course of prolonged and vigorous bicycle riding, in order to avoid penile numbness and impotence.
53Cycling and penile oxygen pressure: the type of saddle matters.PubMed
Ulrich Schwarzer, Frank Sommer, Theodor Klotz, et al.
Eur Urol. 2002 Feb;41(2):139-43. doi: 10.1016/s0302-2838(01)00028-8.
OBJECTIVES: Temporary genital numbness is a common side effect of long-distance cycling; cases of impotence have even been reported. Recent reports have shown that perineal compression leads to a decrease in penile blood flow. Reduced oxygen tension leads to penile fibrosis, which works counterproductively to the achievement of an erection. The shape of the bicycle saddle could be a factor affecting penile perfusion. The aim of this study is to find out the influence of different saddle designs on penile perfusion. MATERIAL AND METHODS: In 20 healthy athletic young men (mean age 26.8 years, range 21-31 years) without history of erectile dysfunction, transcutaneous oxygen pressure (PtcO2), which correlates with arterial and tissue PO2, was measured at the glans of the penis using a transcutaneous measurement device. All men were measured in a standing position before cycling, then during cycling in a seated position on a stationary bicycle. Four different bike saddle designs were used: (A) narrow heavily padded seat; (B) narrow seat with medium padding and a V-shaped groove in the saddle nose ("body geometry"); (C) wide unpadded leather seat; (D) women's special wide seat with medium padding and no saddle nose. RESULTS: During cycling in all seats a decrease in penile oxygen pressure could be observed, reflecting perineal compression. But the differences were unexpected: seat (A) mean PtcO2 11.8 mmHg, decrease in initial oxygen pressure 82.4%; seat (B) mean PtcO2 20.8 mmHg, decrease in initial oxygen pressure 72.4%; seat (C) mean PtcO2 25.3 mmHg, decrease in initial oxygen pressure 63.6%; seat (D) mean PtcO2 62.3 mmHg, decrease in initial oxygen pressure 20.3%. CONCLUSIONS: Cycling in a seated position leads to a compression of perineal arteries with a consequent significant decrease in penile perfusion. But, there are unexpected differences between different saddle types. It was possible to demonstrate that the most important factor in safeguarding penile perfusion is not the amount of padding, but rather a saddle width which prevents sufficiently the compression of the perineal arteries.
54Erectile dysfunction after a long-distance cycling event: associations with bicycle characteristics.PubMed
Joseph R Dettori, Thomas D Koepsell, Peter Cummings, et al.
J Urol. 2004 Aug;172(2):637-41. doi: 10.1097/01.ju.0000130749.37731.9f.
PURPOSE: We conducted a prospective cohort study to examine the relationship between bicycle characteristics and the occurrence of erectile dysfunction. MATERIALS AND METHODS: Subjects consisted of 463 cyclists completing a cycling event of at least 320 km who were free of erectile dysfunction before their event. RESULTS: The cumulative incidence of erectile dysfunction after the ride was 4.2% (95% confidence interval [CI] 2.4%-6.8%) and 1.8% (95% CI 0.7%-3.8%) 1 week and 1 month after the event, respectively. Bicycle characteristics associated with an increased risk of erectile dysfunction included a mountain bicycle compared with a road bicycle (risk ratio [RR] 4.1, 95% CI 1.6-12.5), and the relative height of the handlebars parallel with or higher than the saddle compared with the relative handlebar height lower than the saddle (RR 3.0, 95% CI 1.1-9.3). Perineal numbness during the ride was experienced by 31% of the cyclists and was associated with erectile dysfunction (RR 4.4, 95% CI 1.6-12.7). Saddle cutouts were associated with an increased risk of erectile dysfunction among those who experienced numbness (RR 6.0, 95% CI 1.3-27.1), but the association was reversed among those who did not report numbness (RR 0.3, 95% CI 0.0-2.5). CONCLUSIONS: If the associations described are causal, then cyclists on a long-distance ride may be able to decrease the risk of erectile dysfunction by riding a road bicycle instead of a mountain bicycle, keeping handlebar height lower than saddle height and using a saddle without a cutout if perineal numbness is experienced.
55The effect of saddle nose width and cutout on saddle pressure distribution and perceived discomfort in women during ergometer cycling.PubMed
Anna Sofie Larsen, Frederik G Larsen, Frederik F Sørensen, et al.
Appl Ergon. 2018 Jul;70:175-181. doi: 10.1016/j.apergo.2018.03.002. Epub 2018 Mar 20.
The objectives were 1) to design and produce two novel unpadded bicycle saddles with a wide/medium width and partial nose cutout; 2) to investigate the responses on pressure distribution and perceived discomfort in female cyclists. For comparison, a standard saddle was also tested. Nineteen female cyclists pedaled on an ergometer cycle for 20 min with each saddle in a counterbalanced order. A pressure mat measured saddle interface pressure. Discomfort ratings were collected using a visual analogue scale. Total mean saddle pressure remained similar across saddles. The wide saddle increased anterior and decreased posterior mean saddle pressure as compared with the standard (p < .002) and the medium saddle (p < .001). Significantly increased ischial tuberosity discomfort was found for the novel saddles (p < .001), while crotch discomfort was not significantly different between saddles. The medium width saddle appeared to be the best compromise since increased crotch discomfort was avoided and saddle pressures were redistributed. Such design may be suggested as an alternative to traditional saddles for women reporting discomfort in the perineal region.
56A field-based approach for examining bicycle seat design effects on seat pressure and perceived stability.PubMed
Eadric Bressel, Shantelle Bliss, John Cronin
Appl Ergon. 2009 May;40(3):472-6. doi: 10.1016/j.apergo.2008.10.001. Epub 2008 Nov 17.
The purpose of this study was to investigate the effect of various bicycle seat designs on seat pressure and perceived stability in male and female cyclists using a unique field-based methodology. Thirty participants, comprising male and female cyclists, pedaled a bicycle at 118W over a 350m flat course under three different seat conditions: standard seat, a seat with a partial anterior cutout, and a seat with a complete anterior cutout. The pressure between the bicycle seat and perineum of the cyclist was collected with a remote pressure-sensing mat, and perceived stability was assessed using a continuous visual analogue scale. Anterior seat pressure and stability values for the complete cutout seat were significantly lower (p<0.05; 62-101%) than values for the standard and partial cutout designs. These findings were consistent between males and females. Our results would support the contention that the choice of saddle design should not be dictated by interface pressure alone since optimal anterior seat pressure and perceived seat stability appear to be inversely related.
57[Changes in penile blood flow during cycling--how does one prevent a decreased perfusion?].PubMed
F Sommer, U Schwarzer, C Graf, et al.
Dtsch Med Wochenschr. 2001 Aug 24;126(34-35):939-43. doi: 10.1055/s-2001-16582.
BACKGROUND AND OBJECTIVES: An increased incidence of erectile dysfunction has been observed in cycling enthusiasts. Compression of the perineal region during cycling seems to cause decreased penile perfusion. The resulting hypoxaemia in the corpus cavernosum is associated with penile fibrosis, which leads in the long run to erectile dysfunction. This study set out to determine if cycling can cause changes in penile perfusion and, if so, what precautions can be taken to avoid any associated health hazards, including whether various saddle forms and designs might influence penile blood flow. COHORTS AND METHODS: In 100 healthy athletic men (aged 36 +/- 6.2 years) transcutaneous penile oxygen pressure (tpO (2)) at the glans penis was measured during cycling in different positions and with different types of saddle, using a modified Clark oxygen electrode. RESULTS: The penile blood supply decreased significantly during cycling in a seated position. Cycling in a standing or reclining position (on a reclining bicycle) did not lead to any decrease in penile blood flow. Saddle width was the most important factor for ensuring adequate penile perfusion while cycling in a seated position. CONCLUSION: This study demonstrates that changing from a seated to a standing position during cycling leads to a significant increase in penile perfusion. Therefore we suggest frequent changes from a seated to a standing position during cycling. Additionally we suggest taking sufficient breaks during prolonged and vigorous bike tours, in order to avoid any possible health hazards. Another, not yet widespread, alternative for avoiding a reduction in penile blood flow is cycling on a reclining bicycle.
58Association of Bicycle-Related Genital Numbness and Female Sexual Dysfunction: Results From a Large, Multinational, Cross-Sectional Study.PubMed
Hansen Lui, Nnenaya Mmonu, Mohannad A Awad, et al.
Sex Med. 2021 Jun;9(3):100365. doi: 10.1016/j.esxm.2021.100365. Epub 2021 May 25.
INTRODUCTION: Cycling can lead to microtrauma due to increased perineal pressure, possibly contributing to genital numbness and sexual dysfunction in female cyclists. AIM: We aim to explore the associations between cycling characteristics, female genital numbness, and female sexual dysfunction. METHODS: We conducted a cross-sectional study on female cyclists and sexual wellness. Participants were recruited through Facebook® advertisements and online outreach at athletic clubs. Participants were asked about their cycling characteristics, genital numbness, and female sexual function using the Female Sexual Function Index (FSFI). Univariate and multivariable linear and logistic regression were used to assess risk factors for genital numbness and the association between genital numbness and the FSFI. OUTCOME MEASURES: The outcome measures were cycling characteristics, questions regarding numbness (intensity, duration, location), and the FSFI score. RESULTS: Eight-hundred and seventy-five women were included in the study. Total lifetime miles cycled, biking duration, frequency, distance, speed, and biking surface were not significantly associated with genital numbness. Higher handlebar height was associated with less numbness. The prevalence of sexual dysfunction in the cohort was 52%. Genital numbness was significantly associated with sexual dysfunction (OR: 1.43, 95% CI: 1.05 - 1.95). Sub-group analysis for location of numbness demonstrated significant increase in risk for sexual dysfunction in cyclists who described numbness aro`und the perineum (OR: 2.72, 95% CI: 1.05 - 7.02) and the vulva (OR: 1.55, 95% CI: 1.13 - 2.13). There was also a significant increase in the risk of sexual dysfunction in cyclists who reported a longer duration of numbness (OR: 6.58, 95% CI: 2.27 - 19.07). CONCLUSIONS: Genital numbness is common in women who cycle and is associated with increased risk of FSD and lower average sexual response scores on FSFI. Lui H, Mmonu N, Awad MA, et al. Association of Bicycle-Related Genital Numbness and Female Sexual Dysfunction: Results From a Large, Multinational, Cross-Sectional Study. Sex Med 2021;9:100365.
59Genital Pain and Numbness and Female Sexual Dysfunction in Adult Bicyclists.PubMed
Daniel R Greenberg, Yash S Khandwala, Benjamin N Breyer, et al.
J Sex Med. 2019 Sep;16(9):1381-1389. doi: 10.1016/j.jsxm.2019.06.017. Epub 2019 Aug 8.
INTRODUCTION: Bicycle seat pressure on the perineum may impair arousal and clitoral erection, likely contributing to genital pain and numbness experienced by female cyclists. AIM: We aimed to identify the association between genital pain and numbness experienced by female cyclists and female sexual dysfunction (FSD). METHODS: Female cyclists were recruited to complete an online survey using the Female Sexual Function Index (FSFI), a validated questionnaire to assess FSD. Cyclist demographics, experience, preferred riding style, use of ergonomic cycle modifications, and genital discomfort while riding were also queried. Multivariate logistic regression analysis was used to evaluate risk factors of FSD. MAIN OUTCOME MEASURES: The main outcome was FSFI score, which is used to diagnose FSD when the FSFI score is <26.55. RESULTS: Of the survey respondents, 178 (53.1%) completed the survey and FSFI questionnaire. Mean age was 48.1 years (±0.8 standard error [SE]), and the average riding experience was 17.1 years (±0.9 SE). Overall, 53.9% of female cyclists had FSD, 58.1% reported genital numbness, and 69.1% reported genital pain. After adjusting for age, body mass index, relationship status, smoking history, comorbidities, and average time spent cycling per week, females who reported experiencing genital numbness half the time or more were more likely to have FSD (adjusted odds ratio [aOR], 6.0; 95% CI, 1.5-23.6; P = .01), especially if localized to the clitoris (aOR, 2.5; 95% CI, 1.2-5.5; P = .02). Females that reported genital pain half the time or more while cycling also were more likely to have FSD (aOR, 3.6; 95% CI, 1.2-11.1; P = .02). Cyclists experiencing genital pain within the first hour of their ride were more likely to have FSD (aOR, 12.6; 95% CI, 2.5-63.1; P = .002). Frequency and duration of cycling were not associated with FSD. Analysis of FSFI domains found that the frequency of numbness was correlated with decreased arousal, orgasm, and satisfaction during intercourse, whereas the frequency of pain significantly reduced arousal, orgasm, and genital lubrication. CLINICAL IMPLICATIONS: Female cyclists that experience numbness and/or pain have higher odds of reporting FSD. STRENGTHS & LIMITATIONS: Our study includes a validated questionnaire to assess FSD and queries specific characteristics and symptoms of genital pain and genital numbness; however, the study is limited by its cross-sectional survey design. CONCLUSION: This study highlights the need for cyclists to address genital pain and numbness experienced while cycling, and future studies are required to determine if alleviating these symptoms can reduce the impact of cycling on female sexual function. Greenberg GR, Khandwala YS, Breyer BN, et al. Genital Pain and Numbness and Female Sexual Dysfunction in Adult Bicyclists. J Sex Med 2019; 16:1381-1389.
60The association of bicycle-related genital numbness and Sexual Health Inventory for Men (SHIM) score: results from a large, multinational, cross-sectional study.PubMed
Nima Baradaran, Mohannad Awad, Thomas W Gaither, et al.
BJU Int. 2019 Aug;124(2):336-341. doi: 10.1111/bju.14396. Epub 2018 Jun 7.
OBJECTIVE: To assess the association of genital numbness and erectile dysfunction in male cyclists. SUBJECTS AND METHODS: Cyclists were recruited through Facebook advertisements and outreach to sporting clubs. This is a secondary analysis of a larger epidemiological population-based study that examined sexual and urinary wellness in athletes. We queried cycling habits and erectile function using Sexual Health Inventory for Men (SHIM). RESULTS: A total of 2 774 male cyclists were included in the analysis. Amongst cyclists, there was a statistically significant increase in the trend of genital numbness presence with more years of cycling (P = 0.002), more frequent weekly cycling (P < 0.001), and longer cycling distance at each ride (P < 0.001). Less frequent use of padded shorts (odds ratio [OR] 0.14, P < 0.001) and lower handlebar (OR 0.49, P < 0.001) were associated with numbness, but body mass index (BMI) (OR 1.1, P = 0.33) and age (OR 1.2, P = 0.15) were not. In a multivariate logistic regression model, after adjusting for age, BMI, and lifetime miles (calculated by average daily cycling mileage × cycling days/week × cycling years.), there were no statistically significant differences in mean SHIM score between cyclists with and cyclists without numbness (20.3 vs 20.2, P = 0.83). However, interestingly, the subset of cyclists who reported numbness in the buttock reported statistically significantly worse SHIM scores (20.3 vs 18.4, P < 0.001). This association was not present in cyclists who reported numbness in the scrotum, penis, or perineum and remained significant after adjusting for overall biking intensity. CONCLUSION: Cyclists report genital numbness in proportion with biking intensity but numbness is not associated with worse sexual function in this cohort.
61Scrotal subcutaneous temperature is increased by scrotal insulation or whole-body heating, but not by scrotal neck insulation; however, all three heat-stress models decrease sperm quality in bulls and rams.PubMed
Abdallah M Shahat, Jacob C Thundathil, John P Kastelic
J Therm Biol. 2021 Aug;100:103064. doi: 10.1016/j.jtherbio.2021.103064. Epub 2021 Aug 2.
Ruminant testes are ~2-6 °C below body temperature; increased testicular temperature reduces sperm motility and morphology. Our objective was to serially monitor scrotal subcutaneous temperatures during testicular heat stress and relate those to sperm quality. Two experiments were conducted, with temperature sensors surgically implanted in scrotal subcutaneous tissues recording temperatures every 15 min and semen collected and evaluated weekly. After an initial control interval, testicular temperature was increased. In Experiment 1, in two Angus bulls, whole-scrotum insulation for 96 h increased scrotal subcutaneous temperatures by ~2.0-2.5 °C (P < 0.05). Total and progressive motility decreased (P < 0.05) and reached a nadir at Week 3 (~20 and 10%, respectively). Furthermore, morphologically normal sperm and acrosome integrity also decreased significantly, reaching nadirs at Weeks 3 (15%) and 4 (34%). In Experiment 2, 10 Dorset rams were allocated randomly into two equal groups and either: 1) exposed to 28 °C ambient temperature and 30-34% RH for 8 h/d for 4 d; or 2) subjected to scrotal neck insulation that was applied and removed at the same time as the start and completion, respectively, of heat exposures in the other rams. Scrotal subcutaneous temperatures (monitored in three rams per group) were increased in response to whole-body heating (~0.8 °C, P < 0.05), but not significantly changed by scrotal neck insulation. Decreases in sperm quality were generally similar between treatments, with the most profound changes evident 4 wk after heat stress, with ~10 percentage point reductions in both total and progressive motility and ~10 and 20 percentage point decreases in morphologically normal sperm in rams with whole-body heating versus scrotal neck insulation, respectively. In conclusion, scrotal subcutaneous temperature was significantly increased by scrotal insulation or whole-body heating, but not by scrotal neck insulation; however, all three heat-stress models decreased sperm motility and morphology in bulls and rams.
62Review: Testicular vascular cone development and its association with scrotal thermoregulation, semen quality and sperm production in bulls.PubMed
J P Kastelic, G Rizzoto, J Thundathil
Animal. 2018 Jun;12(s1):s133-s141. doi: 10.1017/S1751731118001167.
Several structural and functional features keep bull testes 2°C to 6°C below body temperature, essential for the production of morphologically normal, motile and fertile sperm. The testicular vascular cone (TVC), located above the testis, consists of a highly coiled testicular artery surrounded by a complex network of small veins (pampiniform plexus). The TVC functions as a counter-current heat exchanger to transfer heat from the testicular artery to the testicular vein, cooling blood before it enters the testis. Bulls with increased TVC diameter or decreased distance between arterial and venous blood, have a greater percentage of morphologically normal sperm. Both the scrotum and testes are warmest at the origin of their blood supply (top of scrotum and bottom of testis), but they are cooler distal to that point. In situ, these opposing temperature gradients result in a nearly uniform testicular temperature (top to bottom), cooler than body temperature. The major source of testicular heat is blood flow, not testicular metabolism. High ambient temperatures have less deleterious effects on spermatogenesis in Bos indicus v. Bos taurus bulls; differences in TVC morphology in B. indicus bulls confer a better testicular blood supply and promote heat transfer. There is a long-standing paradigm that testes operate on the brink of hypoxia, increased testicular temperature does not increase blood flow, and the resulting hypoxia reduces morphologically normal and motile sperm following testicular hyperthermia. However, in recent studies in rams, either systemic hypoxia or increased testicular temperature increased testicular blood flow and there were sufficient increases in oxygen uptake to prevent tissue hypoxia. Therefore, effects of increased testicular temperature were attributed to testicular temperature per se and not to secondary hypoxia. There are many causes of increased testicular temperature, including high ambient temperatures, fever, increased recumbency, high-energy diets, or experimental insulation of the scrotum or the scrotal neck. It is well known that increased testicular temperatures have adverse effects on spermatogenesis. Heat affects all germ cells and all stages of spermatogenesis, with substantial increases in temperature and/or extended intervals of increased testicular temperature having the most profound effects. Increased testicular temperature has adverse effects on percentages of motile, live and morphologically normal sperm. In particular, increased testicular temperature increases the percentage of sperm with abnormal morphology, particularly head defects. Despite differences among bulls in the kind and percentage of abnormal sperm, the interval from increased testicular temperature to the emergence of specific sperm defects is consistent and predictable. Scrotal surface temperatures and structural characteristics of the testis and TVC can be assessed with IR thermography and ultrasonography, respectively.
63Amelioration of heat stress-induced damage to testes and sperm quality.PubMed
A M Shahat, G Rizzoto, J P Kastelic
Theriogenology. 2020 Dec;158:84-96. doi: 10.1016/j.theriogenology.2020.08.034. Epub 2020 Sep 8.
Heat stress (HS) occurs when temperatures exceed a physiological range, overwhelming compensatory mechanisms. Most mammalian testes are ∼4-5 °C cooler than core body temperature. Systemic HS or localized warming of the testes affects all types of testicular cells, although germ cells are more sensitive than either Sertoli or Leydig cells. Increased testicular temperature has deleterious effects on sperm motility, morphology and fertility, with effects related to extent and duration of the increase. The major consequence of HS on testis is destruction of germ cells by apoptosis, with pachytene spermatocytes, spermatids and epididymal sperm being the most susceptible. In addition to the involvement of various transcription factors, HS triggers production of reactive oxygen species (ROS), which cause apoptosis of germ cells and DNA damage. Effects of HS on testes can be placed in three categories: testicular cells, sperm quality, and ability of sperm to fertilize oocytes and support development. Various substances have been given to animals, or added to semen, in attempts to ameliorate heat stress-induced damage to testes and sperm. They have been divided into various groups according to their composition or activity, as follows: amino acids, antibiotics, antioxidant cocktails, enzyme inhibitors, hormones, minerals, naturally produced substances, phenolic compounds, traditional herbal medicines, and vitamins. Herein, we summarized those substances according to their actions to mitigate HS' three main mechanisms: oxidative stress, germ cell apoptosis, and sperm quality deterioration and testicular damage. The most promising approaches are to use substances that overcome these mechanisms, namely reducing testicular oxidative stress, reducing or preventing apoptosis and promoting recovery of testicular tissue and restoring sperm quality. Although some of these products have considerable promise, further studies are needed to clarify their ability to preserve or restore fertility following HS; these may include more advanced sperm analysis techniques, e.g. sperm epigenome or proteome, or direct assessment of fertilization and development, including in vitro fertilization or breeding data (either natural service or artificial insemination).
64Elevated scrotal temperature, but not varicocele grade, reflects testicular oxidative stress-mediated apoptosis.PubMed
Koji Shiraishi, Hiroshi Takihara, Hideyasu Matsuyama
World J Urol. 2010 Jun;28(3):359-64. doi: 10.1007/s00345-009-0462-5. Epub 2009 Aug 5.
PURPOSE: Elevation of scrotal temperature has been known as a cause of male infertility but the exact mechanism leading to impaired spermatogenesis is unknown. This work aimed to investigate the role of elevated scrotal temperature, oxidative stress, and apoptosis in testes of infertile males associated with varicocele. METHODS: Thirty-two testicular biopsies from patients with left varicocele who underwent preoperative measurement of scrotal temperature (DeltaT), serum follicle stimulating hormone (FSH), luteinizing hormone, and testosterone were included. Generation of 4-hydroxy-2-nonenal (4-HNE)-modified proteins and proteolytic fragments of poly(ADP-ribose) polymerase (PARP) and caspase-3 detected by Western blotting were examined as markers for oxidative stress and apoptosis, respectively. These expressions were compared with clinical parameters. RESULTS: Irrespective of varicocele grades, sperm concentration, motility, serum FSH, and testosterone were deteriorated with the increase of DeltaT. There was a distinct correlation between generation of 4-HNE-modified proteins and DeltaT, indicating a close association between scrotal temperature and oxidative stress. Cleavages of PARP and caspase-3, which appear at 86 and 17 kDa, respectively, were strongly correlated with DeltaT and generation of 4-HNE-modified proteins. CONCLUSIONS: Elevation of scrotal temperature is one of the major factors to impair spermatogenesis and steroidogenesis in testis with varicocele. This heat stress is shown to be closely associated with oxidative stress, following the apoptosis of germ cells.
65Physical activity and male reproductive function.PubMed
Farhanah Mohd Hamim, Damayanthi Durairajanayagam, Suzanna Binti Daud, et al.
Reprod Fertil Dev. 2025 Feb;37. doi: 10.1071/RD24196.
Fecundity is declining in humans, which is partly due to male infertility. Poor sperm parameters, the main contributors to male infertility, are associated with sedentary, unhealthy lifestyle and poor dietary habits. Long periods of sedentary work lead to visceral adiposity and persistently elevated scrotal temperatures, which adversely affect spermatogenesis. Apart from increasing scrotal temperatures, excessive visceral adiposity exacerbates adipocyte dysfunction with increased pro-inflammatory adipokine release, like leptin. These, together with the increased scrotal temperature, are responsible for the poor sperm quality. The importance of regular physical activity in male fertility remains a matter of debate, as not all forms of exercises have been found to benefit sperm function. Sperm parameters are, nevertheless, somewhat better in active than in sedentary men. It now appears that low-to-moderate intensity exercises are more beneficial for male reproductive health than high-intensity exercises, which have a negative effect on spermatozoa. Low-to-moderate intensity exercises, in general, improve the overall organ-system function in the body, improve the management of body weight and oxidative stress, consequently improving sperm parameters. The detrimental effects of high-intensity exercises on spermatozoa result from disruption in the hypothalamus-pituitary-gonadal-axis, raised testicular temperature and increased oxidative stress. It, therefore, seems that not all types of exercises are beneficial for male reproductive health. Although some low-to-moderate intensity exercises improve male reproductive function, there remains a need to identify the best form of low-to-moderate intensity exercises, particularly those that do not increase testicular temperature or oxidative stress, to help maintain normal body weight and male reproductive health.
66Relationships between climate and sperm quality in dairy bull semen: A retrospective analysis.PubMed
M Sabés-Alsina, N Lundeheim, A Johannisson, et al.
J Dairy Sci. 2019 Jun;102(6):5623-5633. doi: 10.3168/jds.2018-15837. Epub 2019 Mar 21.
The aim of the present study was to make a retrospective analysis of the relationship between climatic factors and sperm quality of frozen-thawed semen from bulls kept in temperate climates. Semen samples from 21 European dairy bulls from 2 countries were collected and cryopreserved in winter, spring, and summer. Sperm quality parameters such as kinematics, morphology, plasma membrane integrity, mitochondrial membrane potential, sperm chromatin structure assay, and reactive oxygen species were analyzed and correlated retrospectively with climate factors recorded by the local meteorological office. This study demonstrated that sperm quality parameters are more likely to be correlated with climate factors 1 or 2 mo before semen collection than in the month of semen collection. During the month of sperm collection, sperm kinematics, DNA fragmentation, and hydrogen peroxide production were the only sperm quality parameters related to climate factors, whereas 1 and 2 mo before sperm collection, normal morphology and additional sperm kinematics, in addition to DNA fragmentation and hydrogen peroxide production, were correlated with climate factors. In conclusion, dairy bull sperm quality is affected by climatic conditions, even in so-called temperate zones. The timing of heat stress during spermatogenesis determines which aspects of sperm quality are likely to be affected. Husbandry conditions for bulls used for semen collection should be adapted to allow the animals' physiological responses for temperature regulation within the scrotum to operate fully, to mitigate the effects of increased temperature and humidity. Extremes of temperature should be avoided.
67Influence of moderate cycling on scrotal temperature.PubMed
A Jung, P Strauss, H J Lindner, et al.
Int J Androl. 2008 Aug;31(4):403-7. doi: 10.1111/j.1365-2605.2007.00783.x.
Testicular temperature highly correlates with scrotal temperature. It has been postulated that cycling is associated with increased scrotal temperatures with time and consecutively with impaired semen quality. The aim of this study was to evaluate the influence of moderate cycling on scrotal temperature during highly standardized conditions in an experimental lab. A total of 25 volunteers without a history of infertility and normal andrological examination were included for scrotal temperature evaluation. Scrotal temperatures were measured every minute with a portable data recorder connected with two thermistor temperature sensors, which were attached on either side of the scrotum. A further thermistor sensor was attached on the central surface of the bicycle saddle. Ambient temperature in the study room was adjusted to 22 degrees C throughout the whole experiment. All volunteers started the experiment at the same daytime. Clothing of the volunteers consisted of standardized cotton wool trousers and shirts fitting to body size. After acclimatization to the study room in a sitting posture, each volunteer cycled on an exercise cycle for 60 min with a power of 25 Watt representing a speed of 25.45 km/h respectively. The saddle surface temperature reached in the median 35.59 degrees C after 60 min cycling. Median values of scrotal temperatures increased from 35.75 degrees C at the beginning to 35.82 degrees C after 60 min for the left side and from 35.50 to 35.59 degrees C for the right side. No correlation between cycling duration and scrotal temperatures could be found using multivariate anova for repeated measurements. However, scrotal temperatures during cycling were significantly lower (p < 0.001) compared with the last 10 min in sitting posture before starting cycling with a difference of 1.31 degrees C for the left and 1.46 degrees C for the right side. The present study suggests that moderate cycling under standardized conditions with a power of 25 Watt is not a major genital heat stress factor.
68Reproductive function in male endurance athletes: sperm analysis and hormonal profile.PubMed
A Lucía, J L Chicharro, M Pérez, et al.
J Appl Physiol (1985). 1996 Dec;81(6):2627-36. doi: 10.1152/jappl.1996.81.6.2627.
The purpose of this investigation was to study the effects of endurance exercise on male reproductive function (sex hormones and seminograms). Professional cyclists [n = 12; mean age 24 +/- 2 (SD) yr], elite triathletes (n = 9; 26 +/- 3 yr), recreational marathon runners (n = 10; 32 +/- 6 yr), and sedentary subjects (control group; n = 9; 30 +/- 4 yr) were selected as subjects. for each group, the following parameters were measured three times during the sports season (training period: winter; competition period: spring; resting period: fall): percentage of body fat, hormonal profile (resting levels of follicle-stimulating hormone, luteinizing hormone, total and free testosterone, and cortisol), and seminograms (quantitative parameters sperm volume and sperm count; qualitative parameters: sperm motality and morphology). The following comparisons were made in the measured parameters: 1) within groups (longitudinal design) and 2) between groups in each of the three periods (cross-sectional design) and over time (mixed design). In addition, both the volume and the intensity of training of each subject during the season (except for the control group) were quantified. Despite significant differences in training characteristics and in body fat percent, in general no significant differences (P > 0.05) were found in hormonal profiles or in semen characteristics between or within groups. A lower sperm motility (46.2 +/- 19.5%), however, was observed in the cyclists during the competition period when compared either with the other groups during this same period (P < 0.05) or with themselves during the other two periods of study (P < 0.01). In any case, the later phenomenon was attributed to physical factors associated with cycling, such as mechanical trauma to the testis and/or increased gonadal temperature. In conclusion, our findings suggest that endurance exercise does not adversely affect the hypothalamic-pituitary-testis axis.
69Are boxer shorts really better? A critical analysis of the role of underwear type in male subfertility.PubMed
R Munkelwitz, B R Gilbert
J Urol. 1998 Oct;160(4):1329-33.
PURPOSE: Elevation of testicular temperature may result in arrest of spermatogenesis, abnormal semen parameters and sterility. It has been proposed that brief style underwear may produce scrotal hyperthermia and lead to clinical subfertility. Although this idea is regarded as dogma by many in the lay community and the changing of underwear type is a therapy frequently recommended by medical practitioners, there is a paucity of data measuring scrotal temperature as a function of underwear type. MATERIALS AND METHODS: Scrotal, core and skin temperatures were measured in 97 consecutive men presenting for evaluation of primary clinical subfertility. These cases were categorized by underwear type to boxer or brief group. Semen analyses were obtained in all patients. Individuals from each group were compared to ascertain differences in temperature when wearing and not wearing underwear. Baseline semen parameters also were compared. In 14 subjects (crossover group) underwear type was changed to the alternative type and scrotal temperature measurements were repeated. Literature regarding underwear type, testicular temperature and/or fertility was reviewed and critically analyzed. RESULTS: Mean scrotal temperature plus or minus standard deviation was 33.8 +/- 0.8 C and 33.6 +/- 1.1 C in the boxer and brief group, respectively. There were no significant temperature differences between the groups. Differential temperatures comparing core to scrotal temperature and semen parameters also were not significantly different. These observations remained constant in the crossover group. CONCLUSIONS: The hyperthermic effect of brief style underwear has been exaggerated. In our study there was no difference in scrotal temperature depending on underwear type. It is unlikely that underwear type has a significant effect on male fertility. Routinely advising infertility patients to wear boxer shorts cannot be supported by available scientific evidence.
70How much does obesity affect the male reproductive function?PubMed
Giuseppe Bellastella, Davide Menafra, Giulia Puliani, et al.
Int J Obes Suppl. 2019 Apr;9(1):50-64. doi: 10.1038/s41367-019-0008-2. Epub 2019 Apr 12.
Obesity is considered a worldwide epidemic disease. Many pathological conditions have been associated to obesity but the evidence relating to impaired fertility in males with obesity are contrasting. The aim of this review was to evaluate the interplay between obesity and male fertility, analyzing evidence from in vitro and in vivo studies to clinical trials. Obesity seems to be responsible of secondary hypogonadism. Here, we propose a new classification including central, peripheral and testicular factors that may affect the hypothalamic-pituitary-gonadal axis. Moreover, some studies demonstrated a direct action of obesity on sperm count and sperm characteristics, mediated by impaired Sertoli cells function, increased scrotal temperature, oxidative stress and accumulation of toxic substances and liposoluble endocrine disruptors in fat tissue. Recent studies have explored obesity-related epigenetic effects in sperm cells which may cause diseases in offspring. Moreover, not only in females but also males, obesity has been linked to reduced outcomes of in vitro fertilization, with a reduction of pregnancy rate and an increase of pregnancy loss. Finally, we reviewed the effects of weight modifications through diet or bariatric surgery on obesity-related reproductive dysfunction. In this regard, several studies have demonstrated that weight loss has been associated with a restoration of gonadal hormones levels.
71Varicocoele and oxidative stress: New perspectives from animal and human studies.PubMed
Mazdak Razi, Marziyeh Tavalaee, Farshid Sarrafzadeh-Rezaei, et al.
Andrology. 2021 Mar;9(2):546-558. doi: 10.1111/andr.12940. Epub 2020 Dec 6.
BACKGROUND: Varicocoele (VCL), one of the main causes of male subfertility, negatively affects testicular function. Due to limited access to human testicular tissue, animal model studies have been used to evaluate molecular and, recently, epigenetic changes attributed to pathophysiology induced by VCL. OBJECTIVES: This review aims to provide an update on the latest findings regarding the link between VCL-induced biochemical stress and molecular changes in germ cells and spermatozoa. Endocrine and antioxidant status, testicular chaperone-specific hemostasis failure, altered testicular ion balance, metabolic disorders, and altered carbon cycling during spermatogenesis are among the many features that will be presented. DISCUSSION: Literature review coupled with our own findings suggests that ionic imbalance, hypoxia, hyperthermia, and altered blood flow could lead to severe chronic oxidative and nitrosative stress in patients with VCL leading to defective spermatogenesis and impairment of the integrity of all sperm cell components and compartments down to the epigenetic information they carry. CONCLUSION: Since oxidative stress is an important feature of the reproductive pathology of VCL, therapeutic strategies such as the administration of appropriate antioxidants could be undertaken as a complementary non-invasive treatment line.
72Association between seminal granulysin and malondialdehyde in infertile men with varicocele and the potential effect of varicocelectomy.PubMed
Howyda M Kamal, Asmaa A El-Fallah, Shabieb A Abdelbaki, et al.
Andrologia. 2020 Jul;52(6):e13579. doi: 10.1111/and.13579. Epub 2020 Apr 9.
This study assessed the seminal plasma granulysin and malondialdehyde (MDA) levels in patients suffering from varicocele-associated infertility prior to and after varicocelectomy. This study was conducted on 34 infertile men with varicocele (group A) and same patients after varicocelectomy (group B) and 32 fertile normozoospermic males (group C). A detailed history taking, clinical examination, scrotal doppler ultrasound for varicocele diagnosis and grading, semen analysis and estimation of seminal granulysin and MDA before and after varicocelectomy were done to all participants. The mean (SD) granulysin and MDA levels in patients with varicocele were higher than in controls with highly significant differences. Post-operatively, there was a significant reduction in mean (SD) granulysin and in MDA level. Basal seminal granulysin positively correlated with basal seminal MDA, abnormal forms and negatively correlated with basal sperm count, concentration, and progressive motility. The receiver operating characteristic curve of seminal granulysin and MDA levels were conducted for discrimination between infertility cases with varicocele and control groups. Excellent AUCs were found for both markers (AUC = 0.971, 0.991 respectively). We concluded that high levels of granulysin and MDA in the semen of infertile males with varicocele negatively impact their spermatogenesis. Varicocelectomy leads to the improvement of semen parameters and significantly decreases seminal plasma granulysin and MDA levels. Hence, seminal granulysin and MDA could be used as a prognostic test in infertile patients with varicocele.
73Right-sided scrotal varicocele and its association with malignancy: a multi-institutional study.PubMed
Malak Itani, Benjamin Kipper, Michael T Corwin, et al.
Abdom Radiol (NY). 2021 May;46(5):2140-2145. doi: 10.1007/s00261-020-02840-9. Epub 2020 Nov 5.
PURPOSE: To determine the prevalence of isolated right-sided varicocele due to an obstructing malignancy in patients with no other evidence of malignancy. METHODS: This retrospective, multi-institutional study included a text search for right-sided varicocele in consecutive reports of scrotal ultrasound studies performed between 4/22/1999 and 06/24/2018. Diagnosis was confirmed by a radiologist based on the following criteria: pampiniform plexus vein diameter of ≥ 2 mm, which has augmented flow or increases by ≥ 1 mm on Valsalva. Inclusion criteria for adequate follow-up were (1) abdominopelvic CT or MRI performed within 3 months prior to, or any time after, the ultrasound study; or (2) presence of clinical documentation more than 2 years after the ultrasound date. Exclusion criteria were existing cancer diagnosis in the abdomen or pelvis, epididymo-orchitis, intratesticular or intrascrotal mass, and prior scrotal surgery. Images of available CT or MRI studies were reviewed for presence of any explanation of right-sided varicocele. RESULTS: 210 patients with right-sided varicocele met inclusion and exclusion criteria. 118/210 had abdominopelvic CT or MRI in the assigned timeframe. Of these, no patients had malignancy that could account for right-sided varicoceles. Of the 92/210 patients without CT or MRI but with available clinical follow-up, none had a malignancy that could have caused an isolated right-sided varicocele. There was no underlying malignancy to explain the right-sided varicocele in any of the patients, 0/210, 95% CI [0.0-1.4%]. CONCLUSION: No associated malignancy was found in patients with isolated right-sided varicoceles to support additional imaging for malignancy screening.
74Effect of varicocelectomy on fertility. Indications, techniques and results.PubMed
M Caradonti
Actas Urol Esp (Engl Ed). 2020 Jun;44(5):276-280. doi: 10.1016/j.acuro.2019.10.006. Epub 2020 Mar 26.
We define varicocele as the dilation of the veins that make up the pampiniform plexus, which is made up of three branches, the internal spermatic, deferential and external spermatic. The World Health Organization (WHO) has determined that varicocele is an important cause of male infertility. This has been acknowledged by several studies that have shown this cause-effect relationship. Varicocele does not always generate infertility. In fact, many patients with varicocele are fertile, decreasing their percentage in the progression of the pathology and the association with other factors such as tobacco, marijuana or endocrine disorders (diabetes or hypothyroidism). Infertility is a disease of the reproductive system defined by the failure to achieve a clinical pregnancy after 12 months or more of regular unprotected sexual intercourse (WHO). SURGICAL THERAPEUTICS: Surgery is indicated in cases of grade 3 varicocele (when seen through the scrotal skin and palpable as a 'bag of worms' without Valsalva maneuver), cases of atrophy or growth arrest with volume differences of more than 2cm between testes, when accompanied by pain and alterations in the spermiogram in young patients. CONCLUSION: The presence of varicocele determines the performance of varicocelectomy, with the inguinal approach in its three branches being the approach of preference. The laparoscopic approach will be used in specific cases.
75The Effect of Bicycle Saddle Widths on Saddle Pressure in Female Cyclists.PubMed
Zi-Jun Lin, Hsin-Huan Wang, Chia-Hsiang Chen
J Sports Sci Med. 2023 Sep 1;22(3):425-430. doi: 10.52082/jssm.2023.425. eCollection 2023 Sep.
Choosing an unsuitable bicycle saddle increases the saddle pressure and discomfort during cycling. Women contract sports injuries more easily than men during cycling owing to their anatomy. To investigate the effect of saddle widths on the saddle pressure in female cyclists. Ten healthy women with an average age of 20.7 ± 1.3 years, height of 162 ± and 5.9 cm, weight of 56.1 ± 7.5 kg, and a sciatic bone width of 15.5 ± 1.4 cm were recruited for this study. The distributions of saddle pressure for four different saddle widths (i.e., narrow, moderate, wide, and self-chosen) were recorded using a saddle pressure mat. Participants were instructed to pedal steadily with a frequency of 90 RPM and a load of 150 watts. Thirty seconds of riding data was randomly retrieved for analysis. The trials were conducted with a counter-balanced design to minimize random errors. One-way repeated measures ANOVA was used to compare the saddle pressure of different saddle widths, and the significance level was set at α = 0.05. When wide saddles were used, the maximum and average pressure on the right surface of the posterior ischium were lower than those with narrow (p = 0.001, p = 0.012) and moderate (p = 0.016, p = 0.019) saddles. The area of pressure on the pubic bone was smaller when using a wide saddle than when using narrow (p = 0.005) and moderate (p = 0.018) saddles, and the area of pressure on the right posterior sciatic bone was larger under the wide saddle than under the narrow (p = 0.017) and moderate (p = 0.036) saddles. The average force was greater with the moderate saddle than with the wide (p = 0.008) and self-chosen (p = 0.025) saddles. Using a saddle with a width that is longer than the width of the cyclist's ischium by 1 cm can effectively improve the distribution of saddle pressure during riding, while providing better comfort.
76Gender differences in bicycle saddle pressure distribution during seated cycling.PubMed
James J Potter, Julie L Sauer, Christine L Weisshaar, et al.
Med Sci Sports Exerc. 2008 Jun;40(6):1126-34. doi: 10.1249/MSS.0b013e3181666eea.
INTRODUCTION: The purpose of this study was to investigate the influence of gender, power, hand position, and ischial tuberosity (IT) width on saddle pressure during seated stationary cycling. METHODS: Twenty-two experienced cyclists (11 males and 11 females) were fitted to an adjustable stationary bicycle and pedaled at 100 and 200 W in both the tops and drops hand positions. An instrumented pressure mat was used to record saddle pressure distribution. Normalized force, maximum sensor pressure, and center of pressure were computed for anterior and posterior regions of the saddle. RESULTS: When increasing power from 100 to 200 W, there were significant reductions in normalized force in all saddle regions and maximum pressure in the posterior region. When moving from the tops to drops hand position, centers of pressure in all regions moved forward, normalized force and maximum pressure on the posterior region decreased, and females (but not males) exhibited an increase in normalized force and maximum pressure in the anterior region. Male centers of pressure were farther forward in the anterior and total saddle regions than they were for females. Females exhibited a larger IT width than males. Interindividual differences in IT width were significantly correlated with the posterior center of pressure fore-aft location on the saddle in the tops and drops hand positions and with the width between the posterior left and right centers of pressure in the tops hand position. CONCLUSIONS: There are significant gender-related differences in saddle loading which are important to consider when designing saddles. These differences are especially important when riders are in the handlebar drops and more weight is supported on the anterior pelvic structures.
77Strategies for Reducing the Impact of Cycling on the Perineum in Healthy Males: Systematic Review and Meta-analysis.PubMed
Kamil Litwinowicz, Marcin Choroszy, Anna Wróbel
Sports Med. 2021 Feb;51(2):275-287. doi: 10.1007/s40279-020-01363-z.
INTRODUCTION: Perineal pressure associated with bicycle riding is the cause of several genitourinary pathologies, most notably Alcock's syndrome and subsequent perineal numbness. The possible link between cycling-induced perineal numbness and erectile dysfunction makes the development of strategies for perineal protection in bicycle users critical. OBJECTIVE: To assess the effectiveness of strategies for reducing the impact of cycling on the perineum in healthy males. METHODS: We have conducted a systematic review and a meta-analysis of studies examining various means of reducing the impact of cycling on the perineum under the PRISMA guidelines. RESULTS: Out of 2217 screened studies, 22 met our inclusion criteria, and 6 qualified for meta-analysis. The strategies included various designs of saddles, changes in the cycling position, seat shock absorber, shorts with different padding, using the recumbent bike. Using the no-nose saddle and recumbent bike resulted in a significant reduction of perineal pressure and higher penile oxygen pressure compared with a standard saddle. Indirect evidence supports the protective effect of standing on the pedals every few minutes during cycling. More evidence is needed to support-or dismiss-other strategies. CONCLUSIONS: Current evidence supports the use of no-nose saddles as a mean to reduce the negative impact of cycling on the perineum in healthy males at the cost of worse stability and increase of posterior seat pressure. Standing on the pedals every ten minutes might be an effective and potentially widely applicable strategy. The use of a recumbent bike appears to protect the perineum, but several concerns prevent its widespread use.
78Cutting off the nose to save the penis.PubMed
Steven M Schrader, Michael J Breitenstein, Brian D Lowe
J Sex Med. 2008 Aug;5(8):1932-40. doi: 10.1111/j.1743-6109.2008.00867.x. Epub 2008 May 7.
INTRODUCTION: The average bicycle police officer spends 24 hours a week on his bicycle and previous studies have shown riding a bicycle with a traditional (nosed) saddle has been associated with urogenital paresthesia and sexual dysfunction. AIM: The objective of this study was to assess the effectiveness of the no-nose bicycle saddle as an ergonomic intervention and their acceptance among male bicycle police officers. METHODS: Bicycle police officers from five U.S. metropolitan areas were recruited for this study. Officers completed: (i) the International Index of Erectile Function Questionnaire (IIEF); (ii) computerized pressure measurements at the points of contact on the bicycle; the handlebars, the pedals, and the saddle; (iii) one night of nocturnal Rigiscan assessment; (iv) penile vibrotactile sensitivity threshold assessed by computerized biothesiometery. Officers selected a no-nose saddle for their bicycles and were asked to use the intervention saddle exclusively for 6 months, at which point they were retested. MAIN OUTCOME MEASURES: Perineal pressure, urogenital numbness, penile vibrotactile sensitivity threshold, erectile function as measure by International Index of Erectile Function Questionnaire (IIEF) and Rigiscan. RESULTS: After 6 months, 90 men were reassessed. Only three men had returned to a traditional saddle. The results are presented for those who used the no-nose saddle continuously for 6 months. There was a 66% reduction in saddle contact pressure in the perineal region (P < 0.001). There was a significant improvement in penis tactile sensation (P = 0.015). There was a significant improvement in erectile function assessed by IIEF (P = 0.015). There were no changes noted in the Rigiscan measures. The number of men indicating they had not experienced urogential paresthesia while cycling for the preceding 6 months, rose from 27% to 82% using no-nose saddles. CONCLUSIONS: (i) With few exceptions, bicycle police officers were able to effectively use no-nose saddles in their police work. (ii) Use of no-nose saddles reduced most perineal pressure. (iii) Penile health improved after 6 month using no-nose saddles as measured by biothesiometry and IIEF. There was no improvement in Rigiscan(R) measure after 6 months of using no nose saddles, suggesting that a longer recovery time may be needed..
79The science of cycling: physiology and training - part 1.PubMed
Erik W Faria, Daryl L Parker, Irvin E Faria
Sports Med. 2005;35(4):285-312. doi: 10.2165/00007256-200535040-00002.
The aim of this review is to provide greater insight and understanding regarding the scientific nature of cycling. Research findings are presented in a practical manner for their direct application to cycling. The two parts of this review provide information that is useful to athletes, coaches and exercise scientists in the prescription of training regimens, adoption of exercise protocols and creation of research designs. Here for the first time, we present rationale to dispute prevailing myths linked to erroneous concepts and terminology surrounding the sport of cycling. In some studies, a review of the cycling literature revealed incomplete characterisation of athletic performance, lack of appropriate controls and small subject numbers, thereby complicating the understanding of the cycling research. Moreover, a mixture of cycling testing equipment coupled with a multitude of exercise protocols stresses the reliability and validity of the findings. Our scrutiny of the literature revealed key cycling performance-determining variables and their training-induced metabolic responses. The review of training strategies provides guidelines that will assist in the design of aerobic and anaerobic training protocols. Paradoxically, while maximal oxygen uptake (V-O(2max)) is generally not considered a valid indicator of cycling performance when it is coupled with other markers of exercise performance (e.g. blood lactate, power output, metabolic thresholds and efficiency/economy), it is found to gain predictive credibility. The positive facets of lactate metabolism dispel the 'lactic acid myth'. Lactate is shown to lower hydrogen ion concentrations rather than raise them, thereby retarding acidosis. Every aspect of lactate production is shown to be advantageous to cycling performance. To minimise the effects of muscle fatigue, the efficacy of employing a combination of different high cycling cadences is evident. The subconscious fatigue avoidance mechanism 'teleoanticipation' system serves to set the tolerable upper limits of competitive effort in order to assure the athlete completion of the physical challenge. Physiological markers found to be predictive of cycling performance include: (i) power output at the lactate threshold (LT2); (ii) peak power output (W(peak)) indicating a power/weight ratio of > or =5.5 W/kg; (iii) the percentage of type I fibres in the vastus lateralis; (iv) maximal lactate steady-state, representing the highest exercise intensity at which blood lactate concentration remains stable; (v) W(peak) at LT2; and (vi) W(peak) during a maximal cycling test. Furthermore, the unique breathing pattern, characterised by a lack of tachypnoeic shift, found in professional cyclists may enhance the efficiency and metabolic cost of breathing. The training impulse is useful to characterise exercise intensity and load during training and competition. It serves to enable the cyclist or coach to evaluate the effects of training strategies and may well serve to predict the cyclist's performance. Findings indicate that peripheral adaptations in working muscles play a more important role for enhanced submaximal cycling capacity than central adaptations. Clearly, relatively brief but intense sprint training can enhance both glycolytic and oxidative enzyme activity, maximum short-term power output and V-O(2max). To that end, it is suggested to replace approximately 15% of normal training with one of the interval exercise protocols. Tapering, through reduction in duration of training sessions or the frequency of sessions per week while maintaining intensity, is extremely effective for improvement of cycling time-trial performance. Overuse and over-training disabilities common to the competitive cyclist, if untreated, can lead to delayed recovery.
80Validation of Constant Work Rate Cycling Endurance Time for Use in Chronic Obstructive Pulmonary Disease Clinical Trials.PubMed
Richard Casaburi, Debora Merrill, Nancy Kline Leidy, et al.
Ann Am Thorac Soc. 2024 May;21(5):727-739. doi: 10.1513/AnnalsATS.202305-480OC.
A COPD Foundation working group sought to identify measures of exercise endurance, a meaningful aspect of physical functioning in everyday life among patients with chronic obstructive pulmonary disease (COPD) that is not fully accepted in regulatory decision making, hampering drug development. To demonstrate, as we previously asserted (Casaburi 2022;9:252), that constant work rate cycling endurance time is an appropriate exercise endurance measure in patients with COPD. To validate this assertion, we assembled an integrated database of endurance time responses, including 8 bronchodilator (2,166 subjects) and 15 exercise training (3,488 subjects) studies (Casaburi 2022;9:520). Construct validity was demonstrated: ) peak physiologic and perceptual responses were similar for constant work rate and incremental cycling; ) after bronchodilator therapy, there were greater increases in endurance time in patients with more severe airflow limitation; ) after exercise training, endurance time increases were similar across airflow limitation severities; and ) there were correlations between changes in endurance time and changes in mechanistically related physiologic and perceptual variables. Test-retest reliability was demonstrated, with consistency of changes in endurance time at two time points after the intervention. Responsiveness was confirmed, with significant increases in endurance time after active (but not placebo) bronchodilator therapy, with greater increases seen with more severe airflow limitation and after exercise training. On the basis of regression analysis using multiple anchor variables, the minimum important difference for endurance time increase is estimated to be approximately 1 minute. Constant work rate cycling endurance time is a valid exercise endurance measure in COPD, suitable for contributing to the evaluation of treatment benefit supporting regulatory decision making and evidence-based therapeutic recommendations.
81Exercise training in patients with pulmonary and systemic hypertension: A unique therapy for two different diseases.PubMed
Massimo Leggio, Augusto Fusco, Giorgio Limongelli, et al.
Eur J Intern Med. 2018 Jan;47:17-24. doi: 10.1016/j.ejim.2017.09.010. Epub 2017 Sep 11.
Pulmonary hypertension is a potentially life-threatening condition. Given its evolving definition, the incidence and prevalence of the disease is difficult to define, but registries suggest an increased global awareness. The management of patients with pulmonary arterial hypertension is highly specialised and requires multi-disciplinary input from a range of healthcare professionals, including cardiologists, respiratory physicians, rheumatologists, rehabilitation physicians and cardio-pulmonary physiotherapists. Historically, exercise training in pulmonary hypertension has not been recommended because of safety concerns. However, an increasing number of studies have demonstrated the benefit of exercise training on exercise capacity, peak oxygen consumption and quality of life. Systemic hypertension is one of the most important risk factors for cardiovascular disease, and has been ranked as the leading cause for death and disability worldwide: therefore, adequate control of blood pressure is important for public health. Lowering of blood pressure and prevention of hypertension is in first instance preferable by lifestyle changes. These include weight loss, moderation of alcohol intake, a diet with increased fresh fruit and vegetables, reduced saturated fat, reduced salt intake, reduced stress, and, finally, increased physical activity. With regard to the latter, former guidelines predominantly recommended aerobic exercises such as walking, jogging, and cycling for lowering blood pressure. The main focus of this narrative overview paper is to briefly examine and summarize the benefit of exercise training in patients with pulmonary and systemic hypertension, suggest mechanisms by which exercise may improve symptoms and function and provide evidence-based recommendations regarding the frequency and intensity of exercise in these patients.
82Effects of Increased Muscle Strength and Muscle Mass on Endurance-Cycling Performance.PubMed
Iñigo Mujika, Bent R Rønnestad, David T Martin
Int J Sports Physiol Perform. 2016 Apr;11(3):283-9. doi: 10.1123/IJSPP.2015-0405.
Despite early and ongoing debate among athletes, coaches, and sport scientists, it is likely that resistance training for endurance cyclists can be tolerated, promotes desired adaptations that support training, and can directly improve performance. Lower-body heavy strength training performed in addition to endurance-cycling training can improve both short- and long-term endurance performance. Strength-maintenance training is essential to retain strength gains during the competition season. Competitive female cyclists with greater lower-body lean mass (LBLM) tend to have ~4-9% higher maximum mean power per kg LBLM over 1 s to 10 min. Such relationships enable optimal body composition to be modeled. Resistance training off the bike may be particularly useful for modifying LBLM, whereas more cycling-specific training strategies like eccentric cycling and single-leg cycling with a counterweight have not been thoughtfully investigated in well-trained cyclists. Potential mechanisms for improved endurance include postponed activation of less efficient type II muscle fibers, conversion of type IIX fibers into more fatigue-resistant IIa fibers, and increased muscle mass and rate of force development.