Stroke survivors' difficulty in releasing grasped objects may be attributable not only to impaired finger extension but also to delays in terminating activity in the gripping flexor muscles. This study was undertaken 1) to quantify the time needed to initiate and terminate grip muscular activity following stroke and 2) to examine effects of arm support, grip location, and active muscle stretch on the delays recorded in the paretic hand. Delays in initiation and termination of finger flexor muscle activity in response to an auditory stimulus were measured for both paretic and nonparetic hands of ten stroke survivors with chronic hemiparesis and the dominant hand of five neurologically intact subjects. Additionally, the delays for the paretic hand were recorded while an external arm support was used and after 30 min of active muscle stretch. We found that delays in grip initiation and termination were greatest for the paretic hand (1.9 and 5.0 s), followed by the nonparetic hand (0.5 and 1.6 s), and least for the control hand (0.2 and 0.4 s). Arm support reduced delay in grip termination 37% for the paretic hand. Repeated active muscle stretch resulted in 24% reduced delay in grip initiation and 32% increased delay in grip termination for the paretic hand. Therapies and interventions reducing these delays may improve the ability to grasp and release objects and thus increase functional independence for stroke survivors.
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