Sensory Motor Performance Program (SMPP), Rehabilitation Institute of Chicago, Chicago, Illinois;
J Neurophysiol. 2013 Nov;110(10):2484-96. doi: 10.1152/jn.01013.2012. Epub 2013 Aug 14.
We tested an innovative method to estimate joint stiffness and damping during multijoint unfettered arm movements. The technique employs impulsive perturbations and a time-frequency analysis to estimate the arm's mechanical properties along a reaching trajectory. Each single impulsive perturbation provides a continuous estimation on a single-reach basis, making our method ideal to investigate motor adaptation in the presence of force fields and to study the control of movement in impaired individuals with limited kinematic repeatability. In contrast with previous dynamic stiffness studies, we found that stiffness varies during movement, achieving levels higher than during static postural control. High stiffness was associated with elevated reflexive activity. We observed a decrease in stiffness and a marked reduction in long-latency reflexes around the reaching movement velocity peak. This pattern could partly explain the difference between the high stiffness reported in postural studies and the low stiffness measured in dynamic estimation studies, where perturbations are typically applied near the peak velocity point.
我们测试了一种创新的方法来估计多关节无约束手臂运动中的关节刚度和阻尼。该技术采用脉冲扰动和时频分析来估计手臂在伸展轨迹上的力学特性。每个单一的脉冲扰动在单次伸展的基础上提供连续的估计，使我们的方法非常适合在力场存在的情况下研究运动适应，以及研究运动控制在运动重复性有限的受损个体中的情况。与以前的动态刚度研究相比，我们发现刚度在运动过程中发生变化，达到高于静态姿势控制的水平。高刚度与反射活动增加有关。我们观察到在到达运动速度峰值附近，刚度降低，长潜伏期反射明显减少。这种模式可以部分解释在姿势研究中报告的高刚度和在动态估计研究中测量的低刚度之间的差异，在动态估计研究中，通常在接近峰值速度点施加扰动。
