Paksoy Yasemin, Kpobi David, Henschke Jakob, Risch Lucie, Engel Tilman
University Outpatient Clinic, Sports Medicine and Sports Orthopedics, University of Potsdam, Potsdam, Germany.
Front Sports Act Living. 2024 Aug 21;6:1431607. doi: 10.3389/fspor.2024.1431607. eCollection 2024.
Muscle fatigue, characterized by diminished force production and contraction sustainability, can impair muscle coordination and increase joint instability. Differing force profiles used in fatiguing tasks, such as prolonged eccentric trunk protocols, might provide insights into individualized strategies and resulting spinal stability. Thus, this study assessed individual differences in fatigue characteristics during an eccentric trunk flexion-extension protocol in a population of asymptomatic individuals.
Twelve participants (2 f/10 m, 29 ± 4 years, 78.4 ± 16.9 kg, 1.76 ± 0.10 m) performed an eccentric trunk flexion and extension protocol on an isokinetic dynamometer (45° flexion to 10° extension; 60°/s), with final analysis on 8 participants for trunk flexion and 11 for trunk extension due to data exclusions. Participants engaged in a maximal all-out (AO) task for 2 min. Each participant's torque output (Nm) was assessed on a repetition-by-repetition basis, and smoothened by a moving average of 5 repetitions. Individual time profiles for reaching fatigue thresholds (10%, 15%, 20% and 30% reduction of initial torque output), and inter subject variability (by coefficient of variation, CV in %) were assessed throughout the AO task. Further, percentage torque reduction and variability were assessed at mid (1-minute) and end (2-minute) of task.
On average, for flexor and extensor muscles combined, participants reached a force reduction of 10% within 23.2 ± 19.1 s, of 15% within 44.9 ± 19.6 s, of 20% in 62.4 ± 26.3 s, and of 30% within 79.2 ± 21.8 s. The variability between individuals for the timepoint of reaching the defined torque thresholds was assessed by CV ranged between 23.4% and 103.8% for trunk flexor muscles, and between 28.4% and 56.5% for trunk extensor muscles.
A reduction of up to 20% was seen on average for all participants within 1-minute of eccentric trunk flexion and extension. Different inter-individual force output profiles were seen throughout the AO protocol, potentially related to physiological, skill-based, technical, adaptational, and/or motivational factors. The increase in fatigue resulted in a reduction in variability among individuals. A 2-minute protocol effectively induced pronounced fatigue, offering insights into individual force profiles and strategies.
肌肉疲劳的特征是力量产生和收缩可持续性减弱，会损害肌肉协调性并增加关节不稳定。在疲劳任务中使用的不同力量模式，如长时间的躯干离心运动方案，可能有助于深入了解个性化策略以及由此产生的脊柱稳定性。因此，本研究评估了无症状个体群体在躯干离心屈伸运动方案中的疲劳特征个体差异。
12名参与者（2名女性/10名男性，年龄29±4岁，体重78.4±16.9千克，身高1.76±0.10米）在等速测力计上进行躯干离心屈伸运动方案（从45°屈曲到10°伸展；60°/秒），由于数据排除，最终对8名参与者的躯干屈曲和11名参与者的躯干伸展进行分析。参与者进行2分钟的最大全力（AO）任务。逐次评估每个参与者的扭矩输出（牛顿米），并通过5次重复的移动平均值进行平滑处理。在整个AO任务中评估达到疲劳阈值（初始扭矩输出降低10%、15%、20%和30%）的个体时间曲线，以及个体间变异性（变异系数，CV，百分比）。此外，在任务中期（1分钟）和结束时（2分钟）评估扭矩降低百分比和变异性。
平均而言，屈肌和伸肌综合来看，参与者在23.2±19.1秒内达到力量降低10%，在44.9±19.6秒内达到15%，在62.4±26.3秒内达到20%，在79.2±21.8秒内达到30%。通过变异系数评估达到定义扭矩阈值时间点的个体间变异性，躯干屈肌的变异系数在23.4%至103.8%之间，躯干伸肌的变异系数在28.4%至56.5%之间。
在躯干离心屈伸运动1分钟内，所有参与者平均力量降低高达20%。在整个AO方案中观察到不同的个体间力量输出模式，这可能与生理、技能、技术、适应性和/或动机因素有关。疲劳增加导致个体间变异性降低。一个2分钟的方案有效地诱导了明显的疲劳，有助于深入了解个体力量模式和策略。
