Marion M Susan, Wexler Anthony S, Hull Maury L, Binder-Macleod Stuart A
Biomedical Engineering Program, Bainer Hall, Mechanical Engineering, One Shields Avenue, University of California, Davis, California 95616, USA.
Muscle Nerve. 2009 Oct;40(4):573-81. doi: 10.1002/mus.21459.
Mathematical models have been developed to predict fatigue during functional electrical stimulation, but the predictive accuracy at different muscle lengths is unknown. The objectives of our study were to: (1) experimentally determine the relationship between knee extension angle (20 degrees, 40 degrees, 65 degrees, and 90 degrees) and fatigue of the quadriceps muscles, and (2) predict that relationship using a mathematical model. A computer-controlled stimulator sent trains of pulses to surface electrodes on the thighs of five subjects while forces were measured at the ankle. A two-component mathematical model was developed. One component accounted for force, and the other accounted for fatigue. The model was fit to the data, and parameters were identified at 90 degrees . The fitted subject-averaged r(2) value was 0.89. The model was used to predict fatigue at the remaining angles, and the subject-averaged r(2) values were >0.75. Therefore, at least 75% of the variability in the measurements was explained by the model. The force model is explicitly dependent on angle, and the fatigue model is explicitly dependent on force; therefore, the dependence of fatigue on knee angle was implicit.
已经开发出数学模型来预测功能性电刺激期间的疲劳情况，但不同肌肉长度下的预测准确性尚不清楚。我们研究的目的是：（1）通过实验确定膝关节伸展角度（20度、40度、65度和90度）与股四头肌疲劳之间的关系，以及（2）使用数学模型预测这种关系。一台计算机控制的刺激器向五名受试者大腿上的表面电极发送脉冲序列，同时在脚踝处测量力。开发了一个双组分数学模型。一个组分用于描述力，另一个组分用于描述疲劳。该模型与数据进行拟合，并在90度时确定参数。拟合后的受试者平均r(2)值为0.89。该模型用于预测其余角度下的疲劳情况，受试者平均r(2)值>0.75。因此，该模型解释了测量中至少75%的变异性。力模型明确依赖于角度，疲劳模型明确依赖于力；因此，疲劳对膝关节角度的依赖性是隐含的。
