Humboldt-University Berlin, Department of Training and Movement Sciences, Berlin, Germany.
J Biomech. 2010 Dec 1;43(16):3073-9. doi: 10.1016/j.jbiomech.2010.08.014. Epub 2010 Sep 21.
The purpose of the current study in combination with our previous published data (Arampatzis et al., 2007) was to examine the effects of a controlled modulation of strain magnitude and strain frequency applied to the Achilles tendon on the plasticity of tendon mechanical and morphological properties. Eleven male adults (23.9 ± 2.2 yr) participated in the study. The participants exercised one leg at low magnitude tendon strain (2.97 ± 0.47%), and the other leg at high tendon strain magnitude (4.72 ± 1.08%) of similar frequency (0.5 Hz, 1s loading, 1s relaxation) and exercise volume (integral of the plantar flexion moment over time) for 14 weeks, 4 days per week, 5 sets per session. The exercise volume was similar to the intervention of our earlier study (0.17 Hz frequency; 3s loading, 3s relaxation) allowing a direct comparison of the results. Before and after the intervention ankle joint moment has been measured by a dynamometer, tendon-aponeurosis elongation by ultrasound and cross-sectional area of the Achilles tendon by magnet resonance images (MRI). We found a decrease in strain at a given tendon force, an increase in tendon-aponeurosis stiffness and tendon elastic modulus of the Achilles tendon only in the leg exercised at high strain magnitude. The cross-sectional area (CSA) of the Achilles tendon did not show any statistically significant (P > 0.05) differences to the pre-exercise values in both legs. The results indicate a superior improvement in tendon properties (stiffness, elastic modulus and CSA) at the low frequency (0.17 Hz) compared to the high strain frequency (0.5 Hz) protocol. These findings provide evidence that the strain magnitude applied to the Achilles tendon should exceed the value, which occurs during habitual activities to trigger adaptational effects and that higher tendon strain duration per contraction leads to superior tendon adaptational responses.
本研究旨在结合我们之前发表的数据（Arampatzis 等人，2007），探讨对跟腱施加控制调制应变幅度和应变频率对跟腱机械和形态特性可塑性的影响。11 名男性成年人（23.9±2.2 岁）参加了这项研究。参与者在低应变幅度（2.97±0.47%）的腿上进行运动，在高应变幅度（4.72±1.08%）的腿上进行类似频率（0.5 Hz，1s 加载，1s 松弛）和运动容量（跖屈力矩随时间的积分）的运动，每周 4 天，每天 5 组，持续 14 周。运动容量与我们早期研究的干预相似（0.17 Hz 频率；3s 加载，3s 松弛），可以直接比较结果。干预前后，通过测力计测量踝关节力矩，通过超声测量肌腱-腱膜伸长，通过磁共振成像（MRI）测量跟腱横截面积。我们发现，在给定的肌腱力下，应变减小，跟腱-腱膜刚度增加，跟腱弹性模量增加，仅在高应变幅度的腿上进行运动。跟腱的横截面积（CSA）在两腿均未显示出任何统计学上显著的（P>0.05）与运动前值的差异。结果表明，低频（0.17 Hz）比高频（0.5 Hz）方案更能改善肌腱特性（刚度、弹性模量和 CSA）。这些发现提供了证据，即施加在跟腱上的应变幅度应超过习惯性活动中发生的应变幅度，以触发适应性效应，并且每收缩的更高的肌腱应变持续时间会导致更优的肌腱适应性反应。
