Effect of grip location, arm support, and muscle stretch on sustained finger flexor activity following stroke

After gripping an object with the affected hand, stroke survivors may experience difficulty in relaxing the hand to release the object. The goals of this study were: 1) to quantify the severity of this problem by measuring the time needed to terminate a grip activity (grip termination time) and 2) to examine the effect of factors such as grip location, external arm support, and muscle stretch on grip termination time for the affected hand. Ten subjects with chronic hemiparesis subsequent to stroke grasped a cylinder with maximum effort for 5 seconds and then attempted to relax the fingers as quickly as possible. Finger flexor muscle activity was recorded. Grip termination time was defined as the time required for the finger flexor activity to drop to the initial (pre-exertion) level. Grip termination time for the affected hand (6.1 seconds) was three times greater than that for the unaffected hand (2.1 seconds). Reduction of required activation of proximal arm muscles through use of a gravity-compensating arm orthosis decreased the grip termination time for the affected hand (p<0.05). Conversely, active muscle stretch increased grip termination time. Therapies and treatment methods which reduce the delay in terminating finger flexor muscle activity may increase functional independence for stroke survivors.