Volitional Control of the Paretic Hand Post-Stroke Increases Finger Stiffness and Resistance to Robot-Assisted...

Area of Science:

• Neuroscience
• Rehabilitation Engineering
• Biomechanics

Background:

• Individuals post-stroke often exhibit increased muscle tone and abnormal synergies in the paretic upper extremity, complicating hand function and assistive device use.
• Volitional effort to control assistive devices can exacerbate these motor impairments, posing challenges for effective rehabilitation and functional task completion.

Purpose of the Study:

• To investigate the impact of volitional effort on finger stiffness during robot-assisted hand movements in chronic stroke survivors.
• To quantify changes in finger resistance associated with active user engagement compared to passive stretching and sustained exertion.

Main Methods:

• Experiments were conducted with three chronic stroke survivors using EMG-controlled robotic assistance for hand movements.
• Measurements focused on changes in finger stiffness during active, volitional effort to open/close the hand versus passive stretching.
• Evaluated effects of sustained active engagement on muscle tone and resistance over time.

Main Results:

• Active engagement of the upper extremity significantly increased finger muscle tone compared to passive stretching.
• Volitional effort led to greater increases in finger stiffness than sustained exertion over time.
• Results indicate a pronounced effect of user intent on motor output and resistance.

Conclusions:

• Active user effort substantially elevates finger stiffness in stroke survivors, more so than passive stretching or prolonged activity.
• Assistive and rehabilitative device designs should account for heightened finger stiffness during ipsilateral EMG-controlled, user-driven operation.
• Understanding effort-induced stiffness is crucial for optimizing control strategies in upper extremity assistive technology for stroke recovery.