Zhang L Q, Rymer W Z
Sensory Motor Performance Program, Rehabilitation Institute of Chicago, IL 60611, USA.
IEEE Trans Biomed Eng. 1997 Dec;44(12):1192-209. doi: 10.1109/10.649991.
The naturally coexisting intrinsic mechanical and reflex properties of the human elbow joint were identified simultaneously using nonlinear, time-delay, continuous-time, and dynamic models. Angular random perturbations of small amplitude and low bandwidth were applied to the joint using a computer-controlled servomotor, while the subject maintained various levels of mean background muscle torque. Joint neuromuscular dynamics were identified from the measured elbow angle and torque. Stretch reflexes were modeled nonlinearly with both dynamic and static reflex gains. A continuous-time system identification method was developed to estimate parameters of the nonlinear models directly from sampled data while retaining realistic physical or physiological interpretations. Results from six subjects showed that dynamic stretch reflex gains, joint stiffness, and viscosity generally increased with mean background muscle torque; and that dynamic stretch reflex gain was higher during muscle stretch than that during muscle shortening. More importantly, the study provided realistic simultaneous estimates of the relative contributions of intrinsic mechanical and reflex actions to net joint torque. In particular, reflexively-mediated stiffness generated a significant portion of the total joint stiffness and the percentage varied systematically with background muscle torque.
利用非线性、时滞、连续时间和动态模型，同时识别了人体肘关节自然共存的内在力学和反射特性。使用计算机控制的伺服电机对关节施加小幅度、低带宽的角随机扰动，同时受试者保持不同水平的平均背景肌肉扭矩。从测量的肘关节角度和扭矩中识别关节神经肌肉动力学。用动态和静态反射增益对牵张反射进行非线性建模。开发了一种连续时间系统识别方法，可直接从采样数据中估计非线性模型的参数，同时保留现实的物理或生理学解释。六名受试者的结果表明，动态牵张反射增益、关节刚度和粘性通常随平均背景肌肉扭矩增加；并且肌肉伸展期间的动态牵张反射增益高于肌肉缩短期间。更重要的是，该研究提供了对内在力学和反射作用对净关节扭矩相对贡献的实际同时估计。特别是，反射介导的刚度产生了总关节刚度的很大一部分，并且该百分比随背景肌肉扭矩系统地变化。
