Isokinetic strength and power deficits in the hand following stroke

ObjectiveThe purpose of this study was to compare the torque production in the paretic and non-paretic hands during isokinetic tasks following stroke.MethodsWe compared torque and power production at the MCP joint of chronic stroke survivors during isometric and isokinetic tasks. We also recorded surface electromyography (EMG) activity in the forearm muscles.ResultsIsokinetic torque production at all velocities was less than that produced during isometric trials. Both torque and power produced by the paretic hand was substantially impaired. Deficits were substantially greater in extension than flexion trials. EMG data suggests that excessive co-contraction of agonist and antagonist muscles does not greatly affect isokinetic torque production at the MCP joint.ConclusionsThe fact that movement velocity produces larger deficits in torque and power production may explain why patients who have limited strength impairments still experience functional deficits.SignificanceThis study demonstrates that strength testing of stroke survivors under isometric conditions may underestimate the overall level of impairment.

► Isokinetic torque production is substantially less than isometric torque production in the hemiparetic hand.
► Torque and power deficits increase with velocity and are substantially greater in extension than flexion trials.
► Testing of stroke survivors under isometric conditions may underestimate the level of impairment.