Relative contribution of sensory and motor deficits on grip force control in patients with chronic stroke

Objective This study aimed to characterize grasping behavior in static (weight-dependent modulation and stability of control) and dynamic (predictive control) aspects specifically focusing on the relative contribution of sensory and motor deficits to grip force control in patients with chronic stroke. Methods Twenty-four chronic stroke patients performed three manipulative tasks: five trials of 5-s grasp-lift-holding, 30-s static holding, and vertical dynamic/cyclic oscillation of holding the object. Results Exerted static grip force on the paretic side exhibited statistically greater than that on the non-paretic side. Spearman's rank correlation coefficient revealed that the contribution to static grip force control was larger in sensory deficits than in motor deficits. In addition, the sensory deficit is related to the reduced coupling between grip force and load force, suggesting difficulty in predictive control due to the absence of sensory feedback. Conclusions Given that grip force control involves predictive feedforward and online feedback control, the evaluation of grip force might be an important and feasible evaluation manner for the assessment of sensorimotor control in patients post-stroke. Significance Detailed evaluation of grip force control would help to understand the mechanisms underlying hand dysfunction in stroke patients.