Effects of asymmetrical resistance imposed during repeated bilateral upper limb pushing movements on bilateral coordination post-stroke

Abstract

Rehabilitation of the upper limb post-stroke represents a significant challenge with only 5% of severely affected individuals fully recovering function of their arm and hand. This study used a newly designed instrumented bimanual exerciser to assess the effects of an error augmentation (EA) protocol on upper limb bilateral coordination post-stroke. Twenty participants, 10 individuals post-stroke (median age; time post-stroke 60.5 years; 4 months) able to hold a handle (median Chedoke hand 4/7) and 10 healthy controls, volunteered to participate. They were assessed on the bimanual exerciser using an EA protocol (baseline with symmetrical resisted movement at 30% (1 min) and 15% (1 min); adaptation with asymmetrical resistance (15% and 30%: 6 min) and post-adaptation at 15% resistance (3 min). The effects of the EA protocol on bilateral synchronisation when initiating pushing movements were determined. Stroke and healthy participants took the same time to execute the baseline 15% pushing task (median 0.8–1 s). The movement amplitude for the non-paretic arm was greater than for the paretic one (34 cm vs. 30 cm). Stroke participants produced a maximal symmetrical pushing force 25% lower on the paretic side while healthy participants had symmetrical values (7% difference). For both groups, the asymmetric resistance (adaptation) modified the bilateral coordination with increasing onset delays between arms (median values: healthy: 6.4% (55 ms); Stroke: 9.4% (89 ms)). The delays were reversed and differed from baseline at the beginning of the post-adaptation period (post-effects). The large between-subject variability prevented the detection of a difference between groups although the delays were greater overall in post-stroke participants during the adaptation period. Preliminary findings suggest that the EA protocol could modify the timing between movements of the two arms during a bimanual task. Additional data is currently analysed to further understand the potential benefits of training patients with the bimanual exerciser on inter-limb coordination.