| Stroke survivors commonly experience hemiparesis of the arm resulting in deficits such as decreased strength, impaired sensation and increased spasticity. As a result, hemiparetic arm movements are often characterized as lacking coordination, having a reduced range of motion, and consisting of poor endpoint control. The ability to augment sensory afferents to the central nervous system may have the capacity to improve movement control in the hemiparetic arm. To evaluate this phenomenon, tendon vibration was applied to the forearm flexor muscles during planar arm movements made by chronic stroke survivors and neurologically intact control subjects. A two-joint robot was used to evaluate hand position during targeted arm movements and tracking tasks. Additionally, grip pressure and muscle activation was monitored to evaluate changes in arm function that occurred across trial conditions. Initial findings suggested tendon vibration increased stability of the hand at the end of point-to-point movements in stable and unstable work environments. Enhanced arm stability was evidenced by smoother movement trajectory, improved velocity profiles, reduced grip strength and decreased muscle activity. Tendon vibration elicited similar effects in arm stability during a figure-8 tracking task suggesting augmented sensory information has the capacity to improve tasks requiring the integration of error feedback with feedforward control of movement. Increased arm stability elicited by tendon vibration may directly relate to augmented proprioception by improving the quality of sensorimotor integration in the brain and allowing subjects to rely less on visual information for the planning and control of movement. In addition, by increasing cortical activity, tendon vibration may increase cortical modulation of spinal reflexes improving the quality of arm movements for chronic stroke survivors. This study is clinically relevant in that it provides a real-time therapeutic application which can be used to improve stability in the hemiparetic arm. |
