Neuromuscular Electrical Stimulation Improves Walking Performance In People With Multiple Sclerosis

Abstract

Multiple sclerosis (MS) is a neurological disorder that afflicts ~400,000 people in the US. Common symptoms include sensory impairment, fatigue, and reduced mobility. Neuromuscular electrical stimulation (NMES) can be used to restore muscle function and improve mobility, but little is known about the relative influence of pulse width on treatment efficacy. Wider pulse durations (1 ms) activate a greater proportion of sensory axons, whereas narrower durations (0.26 ms) selectively activate motor axons. PURPOSE: To compare the effects of narrow- and wide-pulse NMES on the walking endurance of persons with MS. Wide-pulse NMES (WP) was expected to engage the nervous system more effectively and produce greater gains in walking performance than narrow-pulse NMES (NP). METHODS: Twenty-seven persons with MS (52.6 ± 7.4 yrs) participated in the study. Participants were randomly assigned to two groups: NP group (0.26 ms; 50 Hz; n=13; 54 ± 6.3 yrs), and WP group (1 ms; 100 Hz; n=14; 51.2 ± 8.3). NMES was applied at a tolerable level for 3 sessions/wk for 6 wks. Current was progressively increased to new tolerance and tapered to limit fatigue at testing. NMES was applied to the dorsiflexors and plantar flexors muscles (10 min each muscle, 4 s on and 12 s off) for both legs. Walking endurance (6 MWT) and walking speed (25-FWT) were assessed before (0 wk), after (6 wks), and after a 4 wk retention period (10 wks). RESULTS: Both groups (NP & WP) improved walking endurance and walking speed after the intervention (P values < 0.05). The 6MWT (m) results: NP - before (mean ± SD) = 345 ± 138, after = 387 ± 154, retention = 396 ± 178; WP - before = 409 ± 131, after = 442 ± 155, retention = 450 ± 149. Mixed ANOVA indicated no significant difference between NP and WP groups (P 0.302) in 6MWT. The 25-FWT (s) results (non-parametric test: Friedman test): NP - before (mean ± SE) = 11.9 ± 5.5, after = 9.9 ± 4.4, and retention = 10.5 ± 5.1; WP - no significant differences. Wilcoxon signed rank tests for the changes in walking speed for both groups indicated no statistical difference between the two groups (P values 0.075, 0.173). CONCLUSION: 6 wks of either wide- or narrow-pulse NMES improved walking performance for persons with MS. Wide-pulse NMES didn’t produce greater gain in walking performance than narrow-pulse NMES.