Chronic Effect Of Photobiomodulation Therapy On Muscle Function In Persons With Multiple Sclerosis
MEDICINE AND SCIENCE IN SPORTS AND EXERCISE(2021)
Abstract
Muscle weakness and fatigue are two disabling symptoms of Multiple Sclerosis (MS). Photobiomodulation therapy (PBMT) using red/near-infrared light is an emerging therapeutic modality thought to improve endurance or strength in healthy populations. Previously presented work revealed that a single acute high energy dose of PBMT may improve muscle force recovery in persons with MS (PwMS). PURPOSE: To investigate the effect of extended PBMT at an optimal dose of energy on muscle strength and endurance during a fatiguing contraction in PwMS. METHODS: Randomized crossover design. Persons with mild-moderate relapsing-remitting MS (n = 12, F = 11) were recruited. Participants applied PBMT (active or placebo) to the gastrocnemius and Tibialis Anterior (TA) muscles of both legs twice a day. The optimal dose of energy of the active device for each participant was 40 J, 80 J, or 120 J as determined individually from preliminary studies. The effect of PBMT on muscle function was assessed in five sessions, pre- and post-treatment, and post-washout. The measurements comprised three maximal voluntary contractions (MVCs) of the right TA, followed by an intermittent contraction at 50% MVC to task failure. The measurements were obtained at baseline, after which followed two weeks of active or placebo treatment at home, followed by post-treatment measurements. Then participants had two weeks with no intervention or placebo to wash-off any potential effects, followed by the repetition of the procedure with the other active or placebo device, again followed by two weeks of washout. The Wilcoxon signed-rank test was used to compare the change in pre to post-treatment measurement within subjects and between the active treatment and placebo. Values are mean (SD) in N. RESULTS: Under active treatment, strength significantly improved compared to the baseline (Pre,162.64 (37.51); Post,185.56 (33.95), p = 0.01) and compared to the placebo (Active,22.64 (24.01); Placebo,-4.12 (32.24), p = 0.02). No significant difference in strength was reported with placebo (p = 0.68). Endurance time did not change significantly with either active treatment (p = 0.52) nor placebo (p = 0.85). CONCLUSIONS: Two-week administration of PBMT may improve muscle strength in persons with mild-moderate MS. Supported by a pilot grant from the National MS Society.
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Key words
photobiomodulation therapy,chronic effect,muscle function
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