Impaired force control contributes to car steering dysfunction in chronic stroke

Abstract

Purpose Precise control of a car steering wheel requires adequate motor capability. Deficits in grip strength and force control after stroke could influence the ability steer a car. Our study aimed to determine the impact of stroke on car steering and identify the relative contribution of grip strength and grip force control to steering performance. Methods Twelve chronic stroke survivors and 12 controls performed three gripping tasks with each hand: maximum voluntary contraction, dynamic force tracking, and steering a car on a winding road in a simulated driving environment. We quantified grip strength, grip force variability, and deviation of the car from the center of the lane. Results The paretic hand exhibited reduced grip strength, increased grip force variability, and increased lane deviation compared with the non-dominant hand in controls. Grip force variability, but not grip strength, significantly predicted (R 2 = 0.49, p < 0.05) lane deviation with the paretic hand. Conclusion Stroke impairs the steering ability of the paretic hand. Although grip strength and force control of the paretic hand are diminished after stroke, only grip force control predicts steering accuracy. Deficits in grip force control after stroke contribute to functional limitations in performing skilled tasks with the paretic hand. Implications for rehabilitation Driving is an important goal for independent mobility after stroke that requires motor capability to manipulate hand and foot controls. Two prominent stroke-related motor impairments that may impact precise car steering are reduced grip strength and grip force control. In individuals with mild-moderate impairments, deficits in grip force modulation rather than grip strength contribute to compromised steering performance with the paretic hand. We recommend that driving rehabilitation should consider re-educating grip force modulation for successful driving outcomes post stroke.