The Short-Term Effect of Slope Walking on Soleus H-Reflexes in People with Multiple Sclerosis

•People with Multiple Sclerosis (PwMS) can walk downslope (−7.5%) continuously for 20 min.•DSW is a feasible intervention for PwMS with no observed adverse events and no greater exertion than LW.•DSW induces greater short-term H-reflex depression than level walking or upslope walking. Downslope walking (DSW) causes H-reflex depression in healthy adults, and thus may hold promise for inducing spinal reflex plasticity in people with Multiple Sclerosis (PwMS). The study purpose was to test the hypothesis that DSW will cause acute depression of spinal excitability in PwMS. Soleus H-reflexes were measured in PwMS (n = 18) before and after 20 min of treadmill walking during three visits. Participants walked on a different slope each visit [level: 0% level walking (LW), upslope: +7.5% treadmill walking with an upslope (USW) or downslope: −7.5% (DSW)]. The soleus Hmax/Mmax ratio was used to measure spinal excitability. Heart rate and ratings of perceived exertion (RPE) were measured during walking. DSW induced the largest change in spinal excitability (a 26.7% reduction in soleus Hmax/Mmax (p = 0.001)), although LW also reduced Hmax/Mmax (-5.3%, p = 0.05). Heart rate (p