Preliminary trial of symmetry-based resistance in individuals with post-stroke hemiparesis

We tested a novel control strategy for robotic rehabilitation devices used by individuals with post-stroke hemiparesis. Symmetry-based resistance increases resistance when limb forces become more asymmetric during bilateral exercise. The underlying rationales for the control mode are that it will guide patients to increase paretic limb activation while teaching them to accurately gauge paretic limb force production relative to the non-paretic limb. During a one day training session, seven subjects post-stroke performed lower limb extensions in symmetry-based resistance mode on a robotic exercise machine. Subjects improved lower limb symmetry from 28.6%+/-3.9% to 36.2%+/-4.3% while under symmetry-based resistance training (ANOVA, P = 0.03), but did not maintain the improved lower limb symmetry during a constant resistance post-test. Two subjects that showed the large improvements in symmetry during the one day session performed additional days of training. Those results suggest that some patients demonstrate long lasting benefits with symmetry-based resistance training.