Background: Lower limb strength asymmetry (ie, significant difference between contralateral limbs) has been associated with mobility impairment in persons with multiple sclerosis (MS). However, whether an adaptive exercise modality can be used to modify lower limb strength and potentially improve mobility is unclear. The effect of functional electrical stimulation (FES) cycling on lower limb strength asymmetry in persons with MS with mobility impairment was assessed, and the association between change in lower limb strength asymmetries and changes in functional and self-reported mobility outcomes was explored.

Methods: Eight adults with MS (Expanded Disability Status Scale scores, 5.5–6.5) were included. Outcomes included knee extensor and knee flexor strength asymmetry, Timed 25-Foot Walk (T25FW) test, 2-Minute Walk Test (2MWT), Timed Up and Go (TUG) test, and 12-item Multiple Sclerosis Walking Scale (MSWS-12). Participants received 24 weeks (three times per week) of FES cycling or passive leg cycling.

Results: The FES condition demonstrated a small decrease in knee extensor (d = −0.33) and knee flexor (d = −0.23) strength asymmetry compared with passive leg cycling. With both groups combined, moderate-to-strong associations were observed between change in knee extensor asymmetry and change in T25FW test time (rs = −0.43), 2MWT time (rs = −0.24), TUG test time (rs = 0.55), and MSWS-12 score (rs = 0.43). Moderate correlations were observed between change in knee flexor asymmetry and change in T25FW test time (rs = −0.31), TUG test time (rs = 0.33), and MSWS-12 score (rs = 0.35).

Conclusions: FES cycling may be an efficacious exercise modality for reducing lower limb strength asymmetry and improving mobility in persons with MS.

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