Latash M L
Department of Physical Medicine and Rehabilitation, Rush-Presbyterian St. Luke's Medical Center, Chicago, IL 60612.
Biol Cybern. 1994;71(5):441-50. doi: 10.1007/BF00198920.
A method for reconstructing joint compliant characteristics during voluntary movements was applied to the analysis of oscillatory and unidirectional elbow flexion movements. In different series, the subjects were given one of the following instructions: (1) do not intervene voluntarily; (2) keep the trajectory; (3) in cases of perturbations, return back to the starting position as quickly as possible (only during unidirectional movements). Under the instruction 'keep trajectory', the apparent joint stiffness increased by 50% to 250%. During oscillatory movements, this was accompanied by a decrease in the maximal difference between the actual and equilibrium joint trajectories and, in several cases, led to a change in the phase relation between the two trajectories. The coefficients of correlation between joint torque and angle were very high (commonly, over 0.9) under the 'do not intervene' instruction. They dropped to about 0.6 under the 'keep trajectory' and to about 0.3 under the 'return back' instructions. Under these two instructions, the low values of the coefficients of correlation did not allow reconstruction of segments of equilibrium trajectories and joint stiffness values in all the subjects. The results provide further support for the lambda-version of the equilibrium-point hypothesis and for using the instruction 'do not intervene voluntarily' to obtain reproducible time patterns of the central motor command.
一种用于重建自主运动期间关节顺应性特征的方法被应用于对振荡性和单向性肘部屈曲运动的分析。在不同的系列中，受试者被给予以下指令之一：(1) 不进行自主干预；(2) 保持轨迹；(3) 在受到干扰的情况下，尽快返回起始位置（仅在单向运动期间）。在“保持轨迹”指令下，表观关节刚度增加了50%至250%。在振荡运动期间，这伴随着实际关节轨迹与平衡关节轨迹之间最大差值的减小，并且在某些情况下，导致了两条轨迹之间相位关系的改变。在“不干预”指令下，关节扭矩与角度之间的相关系数非常高（通常超过0.9）。在“保持轨迹”指令下，它们降至约0.6，在“返回”指令下降至约0.3。在这两条指令下，相关系数的低值使得无法在所有受试者中重建平衡轨迹段和关节刚度值。这些结果为平衡点假设的拉姆达版本以及使用“不进行自主干预”指令来获得可重复的中枢运动指令时间模式提供了进一步的支持。
