Effect of altering starting length and activation timing of muscle on fiber strain and muscle damage
Effect of altering starting length and activation timing of muscle on fiber strain and muscle damage
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DOI：
10.1152/japplphysiol.00524.2005
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发表时间：
2006-05-01
影响因子：
3.3
通讯作者：
Herzog, W
中科院分区：
文献类型：
--
作者：
Butterfield, TA;Herzog, W
肌肉拉伤是运动中最常见的损伤之一，在了解其病因方面引起了很大的关注。这些损伤可能是运动过程中反复拉伸（偏心）收缩积累的一系列亚细胞事件的高潮，它们可能受到多种变量的影响，包括纤维应变大小、关节峰值扭矩和起始肌肉长度。为了评估这些变量对体内肌肉损伤程度的影响，我们测量了兔胫骨前肌在重复拉伸-缩短周期中的纤维动力学和关节扭矩产生，在短肌和长肌长度下，同时改变肌肉拉伸前的激活时间。我们发现，当激活时间或开始肌肉长度改变时，肌肉受到恒定肌肉-肌腱单元漂移的重复拉伸-缩短周期的影响，其关节扭矩和纤维应变显着不同。特别是，通过改变激活时间和增加肌肉的起始长度，纤维劳损和肌肉损伤的测量显着增加。然而，我们观察到在循环拉伸缩短运动中对峰值关节扭矩的不同影响，因为增加肌肉的起始长度并没有增加扭矩产生。我们得出结论，在拉伸前改变激活时间和肌肉长度可能会通过显著增加纤维应变大小来影响肌肉损伤，并且在影响肌肉损伤大小方面，纤维动力学是比肌肉-肌腱单元动力学和扭矩产生更重要的变量。
Muscle strain injuries are some of the most frequent injuries in sports and command a great deal of attention in an effort to understand their etiology. These injuries may be the culmination of a series of subcellular events accumulated through repetitive lengthening (eccentric) contractions during exercise, and they may be influenced by a variety of variables including fiber strain magnitude, peak joint torque, and starting muscle length. To assess the influence of these variables on muscle injury magnitude in vivo, we measured fiber dynamics and joint torque production during repeated stretch-shortening cycles in the rabbit tibialis anterior muscle, at short and long muscle lengths, while varying the timing of activation before muscle stretch. We found that a muscle subjected to repeated stretch-shortening cycles of constant muscle-tendon unit excursion exhibits significantly different joint torque and fiber strains when the timing of activation or starting muscle length is changed. In particular, measures of fiber strain and muscle injury were significantly increased by altering activation timing and increasing the starting length of the muscle. However, we observed differential effects on peak joint torque during the cyclic stretch-shortening exercise, as increasing the starting length of the muscle did not increase torque production. We conclude that altering activation timing and muscle length before stretch may influence muscle injury by significantly increasing fiber strain magnitude and that fiber dynamics is a more important variable than muscle-tendon unit dynamics and torque production in influencing the magnitude of muscle injury.