Monti Ryan J, Roy Roland R, Zhong Hui, Edgerton V R
Department of Physiological Science, University of California-Los Angeles, Los Angeles, CA 90095-1761, USA.
J Exp Biol. 2003 Oct;206(Pt 19):3437-45. doi: 10.1242/jeb.00550.
The in vitro mechanical properties of tendons are well described, whereas little data exist for conditions mimicking those found in vivo. Descriptions of the in situ mechanical properties of aponeuroses are more common, but the results are variable. Our goal was to examine the mechanical properties of these tissues under conditions mimicking the in vivo state. Tissue strains were measured in the rat (Rattus norvegicus) soleus muscle directly from the spacing of metal markers implanted within the tissues of interest using an X-ray video microscope. Strains were measured for the tendon and three regions (proximal, middle and distal) of the aponeurosis. Muscle stimulation was accomplished through isolated ventral rootlets, allowing force to be graded in seven repeatable increments independent of muscle-tendon unit length. Peak strains (during maximal tetanic contraction at optimum length; P(o)) were approximately 5% in tendon and approximately 12% in all regions of the aponeurosis. At forces above 50% of P(o), tissue stiffness was nearly constant in all regions, and a pronounced toe region was observed only at forces below approximately 25% of P(o). Stiffness increased in all regions as the muscle-tendon unit was lengthened. These results suggest that using mechanical properties measured ex vivo or during single contractile events in situ to estimate the in vivo behavior of tendon and aponeurosis may lead to errors in estimating the distribution of strain among the contractile and series elastic elements of the muscle.
肌腱的体外力学特性已有详尽描述，然而模拟体内情况的相关数据却很少。关于腱膜原位力学特性的描述较为常见，但结果却不尽相同。我们的目标是在模拟体内状态的条件下研究这些组织的力学特性。使用X射线视频显微镜，通过测量植入感兴趣组织内的金属标记物之间的间距，直接在大鼠（褐家鼠）比目鱼肌中测量组织应变。测量了肌腱和腱膜的三个区域（近端、中部和远端）的应变。通过分离腹侧神经根来实现肌肉刺激，使力能够以七个可重复的增量进行分级，而与肌肉 - 肌腱单元长度无关。峰值应变（在最佳长度下最大强直收缩期间；P(o)）在肌腱中约为5%，在腱膜的所有区域中约为12%。在高于P(o)的50%的力下，所有区域的组织刚度几乎恒定，并且仅在低于约P(o)的25%的力下观察到明显的趾区。随着肌肉 - 肌腱单元的延长，所有区域的刚度均增加。这些结果表明，利用体外测量或原位单次收缩事件期间测量的力学特性来估计肌腱和腱膜的体内行为，可能会在估计肌肉收缩和串联弹性元件之间的应变分布时导致误差。
