Progressive abduction loading therapy targeting flexion synergy to regain reaching function in chronic stroke: Preliminary results from an RCT

Abstract

Reaching function is impaired following stroke due to abnormal coupling of shoulder abduction and elbow flexion. This phenomenon is commonly referred to as flexion synergy, loss of independent joint control, or impaired joint individuation. We have been successful in treating individuals with chronic stroke with moderate to severe motor impairments through the employment of targeted rehabilitation robotics and identified progressive abduction loading as a key element to the rehabilitation of reaching. Here we expand upon the investigation of progressive abduction loading therapy by testing two variants of the exercise in a larger sample and including a 3-month follow-up. Furthermore, we attempt to glean additional insights into the mechanisms underlying improvements by not only assessing reaching distance as a function of abduction loading but, for the first time, assessing peak reaching velocity, a combined measure of dynamic elbow and shoulder strength. Thirty-one participants with severe stroke were randomized to two intervention variants. Preliminary analysis has been performed and results are presented for blinded combined-group data. Following the intervention, there was a significant improvement in both reaching distance and peak reaching velocity. Mechanisms for improvement are briefly discussed.