Background: Muscle weakness is often reported in persons with multiple sclerosis (PwMS) and can contribute to impaired ambulation. Photobiomodulation therapy (PBMT) is a low-level laser therapy thought to improve muscle performance in healthy populations, in part, by enhancing mitochondrial function, and thus might be beneficial in PwMS. A preliminary study showed that a single dose of PBMT may improve muscle force recovery following a fatiguing task of the tibialis anterior (TA) muscle in PwMS.
Objectives: To study the extended effects of PBMT on muscle strength and endurance in persons with mild-moderate relapsing-remitting MS.
Methods: Muscle performance was assessed in 5 sessions, pre- and post-PBMT or Placebo and a post-washout in twelve PwMS (F=11). Muscle measurements comprised 3 maximal voluntary contractions (MVCs) of the right TA muscle followed by a time to task failure intermittent contraction at 50% MVC. After the pre-PBMT measurement, participants applied PBMT (active or placebo) to the belly of TA muscle twice a day for 2 weeks, followed by the post-PBMT measurement. For active PBMT, the optimal dose of energy was 40J, 80J or 120J as determined individually from the preliminary study. Then participants had 2 weeks without any treatment to wash-off any potential effect, followed by the repetition of the procedure with the other of active or placebo treatment, again followed by 2 weeks of washout. Changes in muscle performance from pre- to post-PBMT, and between the active PBMT and placebo was compared using the Wilcoxon signed-rank test. Values are mean (SD).
Results: Strength significantly improved with active PBMT compared to the pre-PBMT (pre,162.64 (37.51) N; post,185.56 (33.95) N; p=0.01). In contrast, no significant change in strength was reported with placebo (pre,177.05 (43.27) N; post,172.93 (35.19) N; p=0.68). Furthermore, strength significantly improved with active treatment compared to the placebo (Active,22.64 (24.01) N; Placebo,-4.12 (32.24) N; p=0.02). No significant improvement in endurance time was reported with either active PBMT (pre,372.36 (265.21) sec; post,464.94 (515.83) sec; p=0.52) or placebo (pre,378.64 (229.38) sec, post,418.97 (444.12) sec; p=0.85).
Conclusions: Preliminary studies suggest that extended PBMT might improve strength in PwMS, and thus might be a novel therapeutic modality to be used independently or in conjunction with other treatments to enhance strength.
Supported by a pilot grant from the National MS Society. Light units were provided by Multi Radiance Medical