Impaired proactive and reactive grip force control in chronic hemiparetic patients

Area of Science:

• Neuroscience
• Rehabilitation Medicine
• Biomechanics

Background:

• Hemiparetic patients often exhibit impaired motor control and hand weakness after stroke.
• Assessing manipulative capacities is crucial for understanding functional recovery and designing effective rehabilitation strategies.

Purpose of the Study:

• To evaluate the grip force adjustments of hemiparetic patients with partial recovery in a drawer task.
• To specifically assess how patients adapt their grip force in response to predictable and unpredictable load perturbations.

Main Methods:

• Participants performed a drawer task involving pulling and holding a manipulandum.
• Load perturbations were applied as short (90 ms) load pulses.
• Grip force, pull force, and electromyographic (EMG) activity were measured during the task.

Main Results:

• Load perturbations elicited rapid grip force and EMG responses, which were larger during holding than pulling.
• Hemiparetic patients demonstrated reduced reactive grip force and EMG responses, dependent on perturbation predictability.
• Proactive grip force scaling before perturbation onset was significantly reduced in patients.
• Coordination between grip and pull forces was impaired in patients, with reduced grip force per unit pull force.

Conclusions:

• Hemiparetic patients exhibit difficulties in both reactive and proactive adaptation to external load disturbances.
• These deficits in grip force control contribute to the functional limitations observed in patients with hemiparesis.
• Findings highlight the need for targeted interventions to improve sensorimotor control and force regulation in stroke rehabilitation.