Neuroscience Research Australia, The University of New South Wales, Sydney, Australia.
J Biomech. 2011 Apr 29;44(7):1334-9. doi: 10.1016/j.jbiomech.2011.01.005. Epub 2011 Feb 1.
Several studies have measured the elastic properties of a single human muscle-tendon unit in vivo. However the viscoelastic behavior of single human muscles has not been characterized. In this study, we adapted QLV theory to model the viscoelastic behavior of human gastrocnemius muscle-tendon units in vivo. We also determined the influence of viscoelasticity on passive length-tension properties of human gastrocnemius muscle-tendon units. Eight subjects participated in the experiment, which consisted of two parts. First, the stress relaxation response of human gastrocnemius muscle-tendon units was determined at a range of knee and ankle angles. Subsequently, passive ankle torque and ankle angle were collected during cyclic dorsiflexion and plantarflexion at a range of knee angles. Viscous parameters were determined by fitting the stress relaxation experiment data with a two-term exponential function, and elastic parameters were estimated by fitting the QLV model and viscous parameters to the cyclic experiment data. The model fitted the experimental data well at slow speeds (RMSE: 1.7 ± 0.5N) and at fast speeds (RMSE: 1.9 ± 0.2N). Muscle-tendon units demonstrated a large amount of stress relaxation. Nonetheless, viscoelastic passive length-tension curves estimated with the QLV model were similar to elastic passive length-tension curves obtained using a model that ignored viscosity. There was little difference in the elastic passive length-tension curves at different loading rates. We conclude that (a) the QLV model can be used to quantify viscoelastic behaviors of relaxed human gastrocnemius muscle-tendon units in vivo, and (b) over the range of velocities we examined, the velocity of loading has little effect on the passive length-tension properties of human gastrocnemius muscle-tendon units.
已有多项研究在体测量了单个人体肌肉-肌腱单元的弹性特性。然而，尚未对单个人体肌肉的黏弹性行为进行表征。本研究采用 QLV 理论来模拟人体比目鱼肌-肌腱单元的黏弹性行为，并确定黏弹性对人体比目鱼肌-肌腱单元被动长度-张力特性的影响。8 名受试者参与了实验，该实验分为两部分。首先，在一系列膝关节角度和踝关节角度下确定人体比目鱼肌-肌腱单元的应力松弛响应。随后，在一系列膝关节角度下进行踝关节背屈和跖屈的循环运动，采集被动踝关节扭矩和踝关节角度。通过将应力松弛实验数据拟合到双指数函数中确定黏滞参数，通过将 QLV 模型和黏滞参数拟合到循环实验数据中确定弹性参数。模型在低速（均方根误差：1.7 ± 0.5N）和高速（均方根误差：1.9 ± 0.2N）下均能很好地拟合实验数据。肌肉-肌腱单元表现出大量的应力松弛。尽管如此，使用 QLV 模型估计的黏弹性被动长度-张力曲线与忽略黏性的弹性被动长度-张力曲线相似。在不同加载速率下，弹性被动长度-张力曲线差异较小。我们得出结论：（a）QLV 模型可用于定量分析人体比目鱼肌-肌腱单元在松弛状态下的黏弹性行为；（b）在我们研究的速度范围内，加载速度对人体比目鱼肌-肌腱单元的被动长度-张力特性影响较小。
