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Neuromuscular Electrical Stimulation Can Improve Walking Endurance In Individuals With Multiple Sclerosis

2016; Lippincott Williams & Wilkins; Volume: 48; Linguagem: Inglês

10.1249/01.mss.0000487142.45225.54

1530-0315

Leah A. Davis, Awad M. Almuklass, Karim Derquaoi, Landon D. Hamilton, Jeffrey R. Hebert, Timothy Vollmer, Enríque Alvarez, Roger M. Enoka,

Muscle activation and electromyography studies

Multiple sclerosis (MS) is a neurodegenerative disease that invariably leads to difficulties with walking. Neuromuscular electrical stimulation (NMES) can be an effective intervention for a range of conditions that reduce motor function. Wide pulses (0.5-1 ms) activate a greater proportion of sensory axons and thereby augment the central contribution to evoked contractions, whereas narrower pulses (0.2-0.4 ms) preferentially activate motor axons. The differential activation of motor and sensory axons is attributable to the longer strength-duration time constant and lower rheobase of sensory axons. PURPOSE: To compare the influence of pulse width on the changes in motor function elicited by a 6-wk NMES intervention in individuals diagnosed with MS. We hypothesized that the improvements in motor function would be greater for participants who received wide-pulse NMES. METHODS: Eleven persons (51.4 ± 6.7 yrs, 5 women) with clinically diagnosed MS participated in a 6-wk NMES intervention. The average score on the first page of the Patient Determined Disease Steps questionnaire was 3.4 ± 1.5. Intervention sessions entailed 10 min of stimulation of the calf muscle and 10 minutes of stimulation of the tibialis anterior muscle. Performance evaluation included a 6-min walk test, a 25-foot walking test, and strength tests of the dorsiflexor and plantarflexor muscles for both limbs. The 6-min walk test provides a measure of walking endurance, whereas the 25-ft walking test indicates fast walking speed. Evaluation sessions were performed at week 0, week 6 (after the 6 wks of treatment), and week 10 (4 wks after intervention). RESULTS: While not yet sufficiently powered to compare the narrow- and wide-pulse groups, the data were collapsed across groups and pairwise comparisons suggested that walking endurance was significantly improved (437 ± 137 m to 464 ± 162 m, P = 0.027) after the intervention (week 6). In contrast, there was no statistically significant change in fast gait speed (5 ± 11 m/s to 4 ± 8 m/s, P = 0.6). Improvements in walking endurance lasted through the retention session (week 0: 453 ± 133 m; week 10: 490 ± 140 m, P<0.01). CONCLUSION: A 6-wk treatment with NMES can improve walking endurance, but not fast walking speed, in persons with MS who self-report walking limitations. Supported by NIH under award number R03HD079508.