Data from: Muscle-tendon unit length changes differ between young and adult sprinters in first stance phase of sprint running

The aim of this study was to compare young and adult sprinters on several biomechanical parameters that were previously highlighted as performance-related and to determine the behaviour of several muscle-tendon units (MTU) in the first stance phase following a block start in sprint running.
The ground reaction force (GRF) and kinematic data were collected from 16 adult and 21 young well-trained sprinters.
No difference between the groups was found in some of the previously-highlighted performance-related parameters (ankle joint stiffness, the range of dorsiflexion and plantar flexor moment). Interestingly, the young sprinters showed a greater maximal and mean ratio of horizontal to total GRF, which was mainly attributed to a greater horizontal GRF relative to body mass and resulted in a greater change in horizontal centre of mass (COM) velocity during the stance phase in the young compared to the adult sprinters.. Results from the MTU length analyses showed that adult sprinters had more MTU shortening and higher maximal MTU shortening velocities in all plantar flexors and the rectus femoris.
Although previously-highlighted performance-related parameters could not explain the greater 100 m sprinting times in the adult sprinters, differences were found in the behaviour of the MTU of the plantar flexors and rectus femoris during the first stance phase. The pattern of length changes in these MTUs provide ideal conditions for the use of elastic energy storage and release for power enhancement.

本研究旨在对比青年与成年训练有素的短跑运动员在多项此前被证实与运动表现相关的生物力学参数上的差异，并探究短跑蹲踞式起跑后首次支撑相内多项肌肌腱单元（MTU）的活动特征。
本研究共采集了16名成年与21名青年训练有素的短跑运动员的地面反作用力（GRF）与运动学数据。
在部分此前被提及的与运动表现相关的参数（踝关节刚度、背屈活动范围及跖屈肌力矩）上，两组运动员未表现出显著差异。
值得注意的是，青年短跑运动员的水平地面反作用力占总地面反作用力的最大比值与平均比值均更高，这主要源于其单位体重的水平地面反作用力更大，进而使得支撑相内青年短跑运动员的水平质心（COM）速度变化幅度高于成年组。
肌肌腱长度分析结果显示，成年短跑运动员的所有跖屈肌及股直肌的肌肌腱缩短幅度更大，且最大缩短速度更高。
尽管此前被证实与运动表现相关的参数无法解释成年短跑运动员100米短跑用时更长的现象，但在首次支撑相内，跖屈肌与股直肌的肌肌腱活动特征存在组间差异。
这些肌肌腱的长度变化模式，为利用弹性储能与释能以提升爆发力提供了理想条件。