股四头肌作等长收缩时的粘弹性分析

Relaxation Properties of Isometric Knee Extension by a Viscoelastic Model

本文用一个粘弹性流变学模型来模拟股四头肌作等长收缩时的松驰过程。在求解非线性松弛函数时，采用了蒙特卡洛，最速下降，牛顿，马柯尔特和共轭梯度法等最优化方法。其结果表明所设的粘弹性模型很好地模拟了股四头肌作等长收缩的松驰过程。两位测试者的Ｅ１和μ比较接近，而对于Ｅ２，运动员约是普通人的２倍。说明运动训练对Ｅ２有显著的影响。在本文优化计算过程中，蒙特卡洛方法是一种有效的方法，其它几种方法由于指数项的存在和因初始参数的不恰当而常常发散。

A viscoelastic rheological model was proposed to simulate the relaxation process of isometric knee extension. Optimization methods such as Monte Carlo,Steepest Descent, Newton's,Marquardt's,and Conjugate Gradient,were employed in the determination of the viscoelastic constants. The results show that the model simulates well the sustainment of knee isometric extension,and the torque curves vs time of knee extending muscles are nonlinear. The torques decrease with time,and in a relatively long period, the torques do not change significantly with time. The torque curves between the ordinary man and sportsman are different significantly. An increase in the maximum tension was achieved by training with contractions which exceeded 90% of the maximum,and the muscular 'reaction'improved. The ratios of the viscoelastic constants E1s and μs between the two men are 1. 03 and 0. 93,whereas the ratio of E2 0. 51. This indicates that the two men have the approximate E1s and μs,and the ordinary man has as half E2 as that of the sportsman. By this viscoelastic modeling,we see the different behaviors of knee extension muscles between ordinary man and sportsman. As for the optimization process,Monte Carlomethod is effective in optimizing the nonlinear relaxation equation,whereas the other optimization methods overflow easily because of the exponential term.