Piovesan D, Casadio M, Mussa-Ivaldi F A, Morasso P G
Sensory Motor Performance Program, Rehab. Institute of Chicago/Northwestern University, Chicago, Illinois, USA.
IEEE Int Conf Rehabil Robot. 2011;2011:5975372. doi: 10.1109/ICORR.2011.5975372.
Impaired arm movements in stroke appear as a set of stereotypical kinematic patterns, characterized by abnormal joint coupling, which have a direct consequence on arm mechanics and can be quantified by the net arm stiffness at the hand. The current available measures of arm stiffness during functional tasks have limited clinical use, since they require several repetitions of the same test movement in many directions. Such procedure is difficult to obtain in stroke survivors who have lower fatigue threshold and increased variability compared to unimpaired individuals. The present study proposes a novel, fast quantitative measure of arm stiffness during movements by means of a Time-Frequency technique and the use of a reassigned spectrogram, applied on a trial-by-trial basis with a single perturbation. We tested the technique feasibility during robot mediated therapy, where a robot helped stroke survivors to regain arm mobility by providing assistive forces during a hitting task to 13 targets covering the entire reachable workspace. The endpoint stiffness of the paretic arm was estimated at the end of each hitting movements by suddenly switching of the assistive forces and observing the ensuing recoil movements. In addition, we considered how assistive forces influence stiffness. This method will provide therapists with improved tools to target the treatment to the individual's specific impairment and to verify the effects of the proposed exercises.
中风后出现的手臂运动障碍表现为一组刻板的运动学模式，其特征是关节耦合异常，这对手臂力学有直接影响，并且可以通过手部的净手臂刚度来量化。目前在功能性任务期间测量手臂刚度的现有方法临床应用有限，因为它们需要在多个方向上对相同的测试动作进行多次重复。与未受损个体相比，中风幸存者疲劳阈值较低且变异性增加，很难进行这样的操作。本研究提出了一种新颖的、快速的运动过程中手臂刚度定量测量方法，即通过时频技术和使用重分配频谱图，在每次试验中施加单个扰动来进行测量。我们在机器人介导的治疗过程中测试了该技术的可行性，在该治疗中，机器人通过在击打任务中为13个覆盖整个可及工作空间的目标提供辅助力，帮助中风幸存者恢复手臂活动能力。在每次击打动作结束时，通过突然切换辅助力并观察随后的反冲运动，估计患侧手臂的端点刚度。此外，我们还考虑了辅助力如何影响刚度。该方法将为治疗师提供更好的工具，以便针对个体的特定损伤进行治疗，并验证所提议练习的效果。
