Fuglevand A J, Winter D A, Patla A E, Stashuk D
Department of Kinesiology, University of Waterloo, Ontario, Canada.
Biol Cybern. 1992;67(2):143-53. doi: 10.1007/BF00201021.
A model of the motor unit action potential was developed to investigate the amplitude and frequency spectrum contributions of motor units, located at various depths within muscle, to the surface detected electromyographic (EMG) signal. A dipole representation of the transmembrane current in a three-dimensional muscle volume was used to estimate detected individual muscle fiber action potentials. The effects of anisotropic muscle conductance, innervation zone location, propagation velocity, fiber length, electrode area, and electrode configuration were included in the fiber action potential model. A motor unit action potential was assumed to be the sum of the individual muscle fiber action potentials. A computational procedure, based on the notion of isopotential layers, was developed which substantially reduced the calculation time required to estimate motor unit action potentials. The simulations indicated that: 1) only those motor units with muscle fibers located within 10-12 mm of the electrodes would contribute significant signal energy to the surface EMG, 2) variation in surface area of electrodes has little effect on the detection depth of motor unit action potentials, 3) increased interelectrode spacing moderately increases detection depth, and 4) the frequency content of action potentials decreases steeply with increased electrode-motor unit territory distance.
开发了一种运动单位动作电位模型，以研究位于肌肉不同深度的运动单位对表面检测到的肌电图（EMG）信号的幅度和频谱贡献。使用三维肌肉体积中跨膜电流的偶极子表示来估计检测到的单个肌纤维动作电位。纤维动作电位模型中包括了各向异性肌肉电导率、神经支配区位置、传播速度、纤维长度、电极面积和电极配置的影响。假设运动单位动作电位是单个肌纤维动作电位的总和。开发了一种基于等电位层概念的计算程序，该程序大大减少了估计运动单位动作电位所需的计算时间。模拟结果表明：1）只有那些肌纤维位于距电极10-12毫米范围内的运动单位才会对表面肌电图贡献显著的信号能量；2）电极表面积的变化对运动单位动作电位的检测深度影响很小；3）增加电极间距会适度增加检测深度；4）动作电位的频率成分随着电极-运动单位区域距离的增加而急剧下降。
