Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, USA.
J Exp Biol. 2012 Oct 15;215(Pt 20):3552-8. doi: 10.1242/jeb.072728. Epub 2012 Jul 5.
The material properties of a tendon affect its ability to store and return elastic energy, resist damage, provide mechanical feedback and amplify or attenuate muscle power. While the structural properties of a tendon are known to respond to a variety of stimuli, the extent to which material properties vary among individual muscles remains unclear. We studied the tendons of six different muscles in the hindlimb of Eastern wild turkeys to determine whether there was variation in elastic modulus, ultimate tensile strength and resilience. A hydraulic testing machine was used to measure tendon force during quasi-static lengthening, and a stress-strain curve was constructed. There was substantial variation in tendon material properties among different muscles. Average elastic modulus differed significantly between some tendons, and values for the six different tendons varied nearly twofold, from 829±140 to 1479±106 MPa. Tendons were stretched to failure, and the stress at failure, or ultimate tensile stress, was taken as a lower-limit estimate of tendon strength. Breaking tests for four of the tendons revealed significant variation in ultimate tensile stress, ranging from 66.83±14.34 to 112.37±9.39 MPa. Resilience, or the fraction of energy returned in cyclic length changes was generally high, and one of the four tendons tested was significantly different in resilience from the other tendons (range: 90.65±0.83 to 94.02±0.71%). An analysis of correlation between material properties revealed a positive relationship between ultimate tensile strength and elastic modulus (r(2)=0.79). Specifically, stiffer tendons were stronger, and we suggest that this correlation results from a constrained value of breaking strain, which did not vary significantly among tendons. This finding suggests an interdependence of material properties that may have a structural basis and may explain some adaptive responses observed in studies of tendon plasticity.
肌腱的材料特性影响其储存和返回弹性能量、抵抗损伤、提供机械反馈以及放大或衰减肌肉力量的能力。虽然肌腱的结构特性已知会对各种刺激做出反应，但个体肌肉之间的材料特性差异程度尚不清楚。我们研究了东方野火鸡后肢的 6 种不同肌肉的肌腱，以确定其弹性模量、最大拉伸强度和回弹性是否存在差异。使用液压试验机测量肌腱在准静态伸长过程中的力，并构建应力-应变曲线。不同肌肉的肌腱材料特性存在很大差异。一些肌腱的平均弹性模量差异显著，6 种不同肌腱的弹性模量值相差近两倍，从 829±140 到 1479±106 MPa。将肌腱拉伸至断裂，并将断裂时的应力，即最大拉伸应力，作为肌腱强度的下限估计值。对其中 4 根肌腱的断裂测试显示，最大拉伸应力存在显著差异，范围为 66.83±14.34 至 112.37±9.39 MPa。回弹性，即循环长度变化中返回的能量分数通常较高，并且测试的 4 根肌腱中的一根在回弹性方面与其他肌腱显著不同（范围：90.65±0.83 至 94.02±0.71%）。对材料特性之间的相关性分析表明，最大拉伸强度与弹性模量呈正相关（r²=0.79）。具体来说，更硬的肌腱更强壮，我们认为这种相关性是由于断裂应变的约束值，而肌腱之间的断裂应变值没有显著差异。这一发现表明，材料特性之间存在相互依存关系，这种关系可能具有结构基础，并可以解释在肌腱可塑性研究中观察到的一些适应性反应。
