Moderate to severe hemiparesis as a result of stroke can have a significant impact upon many common activities of daily living (ADLs), resulting in significant dependence on caregivers. One common occurrence in stroke is the development of abnormal muscle synergies where the elbow, wrist, and fingers involuntarily flex and close when the patient exerts effort to lift the arm. This results in a loss of reach area and closing of the hand, greatly impairing its use. However, it has been shown that when the arm is supported and an outside force is used to lift the arm, this involuntary activity is not elicited. Any intervention to restore arm and hand function in individuals with hemiparesis due to severe to moderate stroke must first address the alleviation of this shoulder-elbow flexion synergy. The objective of the proposed work is to demonstrate the effectiveness of active support of the arm proximal to the elbow to assist shoulder abduction with the long-term goal of developing a small, worn, robotic assistance system. By using an external device rather than the person's voluntary effort to counter gravity, the effects of the shoulder-elbow flexion synergy will be significantly reduced; potentially allowing the user's retained voluntary movement control and strength to be effective. While earlier work has used arm support at the forearm or wrist to show a reduction in flexion synergy, this arrangement is not amenable to a worn device. The research proposed will be achieved through meeting two Specific Aims. The first is to characterize the kinetics, kinematics, and functional capabilities of the post-stroke hemiparetic arm while being supported. This will consist of experiments to test subjects' abilities to produce force isometrically, reach throughout the workspace in front of them, and open the hand with and without arm support provided by a commercially available robotic arm. The second Aim will be to quantify the changes in muscle activity as a result of reduction in abnormal flexion synergy afforded by proximal arm support. This Aim will serve to measure the timing and magnitude changes of EMG signals of the arm flexors as they relate to shoulder muscle EMG activity and quantify and demonstrate the changes in muscle activity that lead to a reduction in abnormal flexion synergy. Similar to Aim 1, EMG patterns will be compared between the gravity supported and the unsupported conditions. The work proposed represents a novel placement of arm support to reduce flexion synergies. This work is critical to the development of future arm assistance systems for individuals with hemiparesis as a result of stroke. By moving the location of the support closer to the body, a lightweight, wearable, clinically deployable, and user acceptable arm support system can be developed in later projects.

Individuals suffering a stroke represent a significant portion of the Veterans Health Administration's overall case load. With the recent conflicts seeing a large increase in traumatic brain injuries compared to previous engagements, the number of veterans suffering from a stroke is likely to increase. Stroke commonly results in permanent neurological damage, severely impacting upper limb function. One common result of a stroke is abnormal joint coordination of the upper limb, where voluntarily lifting the arm at the shoulder causes the elbow, wrist, and fingers to involuntarily flex and close. This can substantially reduce the capability to carry out many activities of daily living, particularly those requiring two hands to perform. The lack of controllable function of the impaired arm can quickly lead to intentional disuse of the limb and withdrawal from professional and social activities.