Karamanidis Kiros, Arampatzis Adamantios
Institute for Biomechanics and Orthopaedics, German Sport University of Cologne, Carl-Diem-Weg 6, 50933, Cologne, Germany.
J Exp Biol. 2005 Oct;208(Pt 20):3907-23. doi: 10.1242/jeb.01830.
The objectives of this work were (i) to investigate whether chronic endurance running is a sufficient stimulus to counteract the age-related changes in the mechanical and morphological properties of human triceps surae (TS) and quadriceps femoris (QF) muscle-tendon units (MTUs) by comparing runners and non-active subjects at different ages (young and old), (ii) to identify adaptational phenomena in running mechanics due to age-related changes in the mechanical and morphological properties of the TS and QF MTUs, and finally (iii) to examine whether chronic endurance-running exercise is associated with adaptational effects on running characteristics in old and young adults. The investigation was conducted on 30 old and 19 young adult males divided into two subgroups according to their running activity: endurance-runners vs non-active. To analyse the properties of the MTUs, all subjects performed isometric maximal voluntary (MVC) ankle plantarflexion and knee extension contractions at 11 different MTU lengths on a dynamometer. The activation of the TS and QF during MVC was estimated by surface electromyography. The gastrocnemius medialis and the vastus lateralis and their distal aponeuroses were visualized by ultrasonography at rest and during MVC, respectively. Ground reaction forces and kinematic data were recorded during running trials at 2.7 m s(-1). The TS and QF MTU capacities were reduced with aging (lower muscle strength and lower tendon stiffness). Runners and non-active subjects had similar MTU properties, suggesting that chronic endurance-running exercise does not counteract the age-related degeneration of the MTUs. Runners showed a higher mechanical advantage for the QF MTU while running (lower gear ratio) compared to non-active subjects, indicating a task-specific adaptation even at old age. Older adults reacted to the reduced capacities of their MTUs by increasing running safety (higher duty factor, lower flight time) and benefitting from a mechanical advantage for the TS MTU, lower rate of force generation and force generation per meter distance. We suggest that the improvement in running mechanics in the older adults happens due to a perceptual motor recalibration and a feed-forward adaptation of the motor task aimed at decreasing the disparity between the reduced capacity of the MTUs and the running effort.
（i）通过比较不同年龄段（年轻和年老）的跑步者和不运动的受试者，调查长期耐力跑步是否足以抵消人小腿三头肌（TS）和股四头肌（QF）肌腱单位（MTU）机械和形态特性的年龄相关变化；（ii）确定由于TS和QF MTU机械和形态特性的年龄相关变化而导致的跑步力学适应性现象；最后（iii）研究长期耐力跑步运动是否与老年人和年轻人跑步特征的适应性影响相关。该研究对30名老年男性和19名年轻男性进行，根据他们的跑步活动分为两个亚组：耐力跑步者和不运动者。为了分析MTU的特性，所有受试者在测力计上于11种不同的MTU长度下进行等长最大自主收缩（MVC）踝关节跖屈和膝关节伸展收缩。通过表面肌电图估计MVC期间TS和QF的激活情况。分别在静息和MVC期间通过超声对腓肠内侧肌、股外侧肌及其远端腱膜进行可视化。在以2.7 m s(-1)的速度进行跑步试验期间记录地面反作用力和运动学数据。随着年龄增长，TS和QF MTU的能力下降（肌肉力量降低和肌腱刚度降低）。跑步者和不运动的受试者具有相似的MTU特性，表明长期耐力跑步运动不能抵消MTU的年龄相关退化。与不运动的受试者相比，跑步者在跑步时QF MTU具有更高的机械优势（传动比更低），表明即使在老年也存在特定任务的适应性。老年人通过提高跑步安全性（更高的负荷率、更短的腾空时间）来应对其MTU能力的下降，并受益于TS MTU的机械优势、更低的力产生速率和每米距离的力产生量。我们认为老年人跑步力学的改善是由于感知运动重新校准和运动任务的前馈适应，旨在减少MTU能力下降与跑步努力之间的差异。
