Ettema G J, van Soest A J, Huijing P A
Vakgroep Functionele Anatomie, Faculteit Bewegingswetenschappen, Vrije Universiteit Amsterdam, The Netherlands.
J Exp Biol. 1990 Nov;154:121-36. doi: 10.1242/jeb.154.1.121.
The influence of series elastic structures on the dynamics of the contractile machinery was examined in the gastrocnemius medialis (GM) of five male Wistar rats, with respect to enhancement of work of a muscle-tendon complex after active stretch. Imposed isotonic and isokinetic contractions were preceded by either an isometric phase (PI) or an active stretch (PS). The effects of fibre length differences at the onset of shortening, due to differences of extension of tendinous structures, were studied. For the isotonic experiments fibre length and shortening velocity were estimated 30 ms after release and compared with the PI length-velocity curve determined at the same force level. For shortening above the optimum length, about half of the enhanced shortening found after prestretch could be explained by PS-PI fibre length differences. Below the optimum length, PS shortening velocity was somewhat lower than expected on the basis of length-velocity characteristics. Enhancement of work output due to stretch was different for isokinetic and isotonic shortening. In isokinetic shortening, following prestretch, fibre work was limited because of enhanced shortening of the tendinous structures. In stretch-shortening cycles imposed on a muscle-tendon complex, the length of the complex affected all prestretch effects, i.e. potentiation of the contractile element, contractile element interaction with the tendinous structures, and elastic energy release. It is concluded that, besides potentiation effects and enhanced elastic energy release, the influence of series elastic structures on fibre dynamics determines active stretch-induced work enhancement. The contribution by these mechanisms to this work enhancement depends largely on the type of stretch-shortening cycle.
在五只雄性Wistar大鼠的腓肠肌内侧头（GM）中，研究了串联弹性结构对收缩机制动力学的影响，涉及主动拉伸后肌肉 - 肌腱复合体功的增强。施加的等张和等速收缩之前分别有一个等长阶段（PI）或主动拉伸（PS）。研究了由于肌腱结构伸展差异导致的缩短开始时纤维长度差异的影响。对于等张实验，在释放后30毫秒估计纤维长度和缩短速度，并与在相同力水平下确定的PI长度 - 速度曲线进行比较。对于超过最佳长度的缩短，预拉伸后发现的增强缩短中约一半可以由PS - PI纤维长度差异来解释。在最佳长度以下，PS缩短速度略低于基于长度 - 速度特性预期的值。等速和等张缩短时，拉伸导致的功输出增强有所不同。在等速缩短中，预拉伸后，由于肌腱结构缩短增强，纤维功受到限制。在施加于肌肉 - 肌腱复合体的拉伸 - 缩短循环中，复合体的长度影响所有预拉伸效应，即收缩元件的增强、收缩元件与肌腱结构的相互作用以及弹性能量释放。得出的结论是，除了增强效应和弹性能量释放增加外，串联弹性结构对纤维动力学的影响决定了主动拉伸诱导的功增强。这些机制对这种功增强的贡献在很大程度上取决于拉伸 - 缩短循环的类型。
