Neuromuscular Research Center, Department of Biology of Physical Activity, University of Jyväskylä, Jyväskylä 40014, Finland.
J Exp Biol. 2012 Oct 15;215(Pt 20):3665-71. doi: 10.1242/jeb.068874.
Overuse-induced injuries have been proposed as a predisposing factor for Achilles tendon (AT) ruptures. If tendons can be overloaded, their mechanical properties should change during exercise. Because there data are lacking on the effects of a single bout of long-lasting exercise on AT mechanical properties, the present study measured AT stiffness before and after a marathon. AT stiffness was determined as the slope of the force-elongation curve between 10 and 80% of maximum voluntary force. AT force-elongation characteristics were measured in an ankle dynamometer using simultaneous motion-capture-assisted ultrasonography. Oxygen consumption and ankle kinematics were also measured on a treadmill at the marathon pace. All measurements were performed before and after the marathon. AT stiffness did not change significantly from the pre-race value of 197±62 N mm(-1) (mean ± s.d.) to the post-race value of 206±59 N mm(-1) (N=12, P=0.312). Oxygen consumption increased after the race by 7±10% (P<0.05) and ankle kinematic data revealed that in nine out of 12 subjects, the marathon induced a change in their foot strike technique. The AT of the physically active individuals seems to be able to resist mechanical changes under physiological stress. We therefore suggest that natural loading, like in running, may not overstress the AT or predispose it to injury. In addition, decreased running economy, as well as altered foot strike technique, was probably attributable to muscle fatigue.
过度使用导致的损伤被认为是跟腱（AT）断裂的一个诱发因素。如果肌腱可以过载，那么它们的机械性能应该会在运动过程中发生变化。由于缺乏单次长时间运动对 AT 机械性能影响的数据，本研究测量了马拉松前后 AT 的刚度。AT 刚度是通过在最大自愿力的 10%到 80%之间的力-伸长曲线来确定的。在跑步机上使用同步运动捕捉辅助超声测量了 AT 力-伸长特性。在马拉松比赛的配速下，还测量了耗氧量和踝关节运动学。所有测量均在马拉松比赛前和比赛后进行。AT 刚度从比赛前的 197±62 N mm(-1)（平均值±标准差）到比赛后的 206±59 N mm(-1)（N=12，P=0.312）没有显著变化。耗氧量在比赛后增加了 7±10%（P<0.05），踝关节运动学数据显示，在 12 名受试者中有 9 名的足着地技术在马拉松比赛中发生了变化。因此，我们认为活跃个体的 AT 似乎能够在生理应激下抵抗机械变化。我们因此认为，像跑步这样的自然负荷可能不会过度拉伸 AT 或使其容易受伤。此外，跑步经济性的降低以及足着地技术的改变可能归因于肌肉疲劳。
