Effect of acute unloaded arm versus leg cycling exercise on the soleus H-reflex in adults with multiple sclerosis

Abstract

This study compared the effect of acute bouts of unloaded arm versus leg cycling exercise on spasticity of the lower legs in persons with multiple sclerosis (MS) and then examined post-activation depression (PAD) as a possible mechanism for the anti-spastic effects of acute exercise. Participants (N=10) had relapsing-remitting MS, slight to moderate spasticity of the soleus muscle, and were independently ambulatory. Spasticity was measured in the soleus muscle using the H-reflex and modified Ashworth scale (MAS). PAD was measured in the soleus muscle based on a simple, standardized protocol for modifying the parameters for evoking the H-reflex. In three separate sessions participants undertook 20min of either unloaded arm cycling exercise, unloaded leg cycling exercise, or control (quiet sitting) conditions in a random order, and data were collected before and after all three conditions. The H-reflex and MAS were significantly decreased after both unloaded arm and leg cycling exercise and significantly increased after quiet sitting. There was no change over time in PAD among the conditions. The reduction in the H-reflex was approximately 50% larger after leg than arm cycling exercise, whereas the reduction in MAS scores was approximately 20% larger after leg than arm cycling exercise. Such findings provide support for anti-spastic potential of both arm and leg cycling exercise on spasticity of the legs, but indicate that the effect is larger for the musculature that is activated during cycling and not explained by PAD.