Does photobiomodulation therapy combined to static magnetic field (PBMT-sMF) promote ergogenic effects even when the non-exercised leg is irradiated? A randomized, triple-blind, placebo-controlled trial.

Abstract Background The direct application of photobiomodulation therapy (PBMT) combined with a static magnetic field (sMF) (PBMT-sMF) to target tissues is shown to improve muscle performance and recovery. Studies have reported possible PBMT induced systemic effects. Notably, the extent of these effects on musculoskeletal performance and the optimal site of application remain unclear, although this information is clinically important because these factors directly affect the magnitude of the effect. We investigated the effects of PBMT-sMF on musculoskeletal performance and post-exercise recovery of muscles in exercised and non-exercised legs before the implementation of an exercise protocol.Methods This randomized, triple-blind placebo-controlled study included 30 healthy men randomly assigned to the placebo, exercised-leg, and non-exercised leg groups. Active or placebo PBMT-sMF was applied to 6 sites of the quadriceps muscle of both legs. An eccentric exercise protocol was used to induce fatigue. The following parameters were analyzed to evaluate exercise performance: peak torque assessed by maximal voluntary contraction (MVC), delayed muscle pain assessed by the visual analogue scale (VAS), muscle injury assessed by serum creatine kinase (CK), and fatigue assessed by serum lactate levels. Evaluations were performed before implementation of the eccentric (baseline) exercise protocol, as well as immediately after and 1, 24, 48, and 72 hours upon protocol completion. The Bonferroni post-hoc ANOVA test was used considering the level of statistical significance p <0.05.Results Compared to the placebo and systemic groups, irradiation with PBMT-SMF led to statistically significant improvement (p <0.05) with regard to all variables in the exercised-leg group. Results of irradiation in the non-exercised leg group were similar to those in the placebo group with regard to all variables.Conclusion Our results support the current evidence that irradiation of all exercised muscles produces ergogenic effects. PBMT-sMF improved performance and reduced muscle fatigue only when applied locally to muscles involved in physical activity.