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Early recovery after stroke is significant for slow emergence of volitional movement. Initial movements are constrained by stereotypical co-activation of muscle groups such as shoulder abductors and distal limb flexors resulting in the loss of independent joint control. The objective of this study was to utilize new quantitative methods to evaluate the emergence and progression of the loss of independent joint control in the acute phase of recovery from stroke. Fifteen participants have been followed a maximum range of 2 to 32 weeks post-stroke. Participants underwent weekly and monthly robotic evaluations of horizontal plane reaching workspace as a function of abduction loading (0%-200% of limb weight). The magnitude of loss of independent joint control, indicated by the rate of work area reduction as a function of abduction loading, was evident even as early as 2 weeks post-stroke. Group analysis indicated that individuals with mild stroke show immediate presence of the impairment with an exponential rate of recovery over time while individuals with severe stroke show persistent impairment. Early detection and quantification of reaching impairments, such as the loss of independent joint control, will allow clinicians to more efficiently identify patients who would benefit from impairment-based targeted interventions. For example, patients with severe loss of independent joint control will likely benefit from early administration of an intervention attempting to reduce abnormal shoulder abductor/distal limb flexor co-activations during reaching. The field of rehabilitation robotics has demonstrated such interventions to be promising in the chronic severe stroke population.

After stroke, arm function can be limited by a reduction in the selectivity of movements, due to involuntary coupling of shoulder abduction and elbow flexion, limiting the ability to reach. Gravity compensation of the arm reduces the required active shoulder abduction torques, which results in a larger range of motion instantaneously. Integration of a motivating rehabilitation game in the training program stimulates motor relearning processes during training. During 6 weeks, 8 chronic stroke survivors received 3 sessions of 30 minutes gravity compensated reach training per week using a rehabilitation game, which was evaluated by assessing motor status and a circle drawing task before and after training. After gravity compensation training, Fugl Meyer scores and the range of motion obtained from the circle drawing task had improved in a seven of the eight chronic stroke survivors. The present findings indicate that gravity compensation in combination with rehab games can be a valuable training modality for stroke rehabilitation.