Effects of photobiomodulation therapy combined with static magnetic field on training adaptations and detraining responses: a randomised placebo-controlled trial.

Objectives: Although photobiomodulation therapy combined with static magnetic field (PBMT-sMF) has demonstrated benefits for enhancing performance and recovery when applied before or after exercise sessions, its effects on adaptations during periods without training after strength training protocols remain unexplored. Therefore, we aimed to evaluate the effects of PBMT-sMF on the maintenance of muscle strength and structural properties of the quadriceps during a 4-week detraining period following a 12-week resistance strength training programme. Methods: In this triple-blind, randomised, placebo-controlled trial, 48 healthy men were randomised to one of four groups: PBMT-sMF during both training and detraining, PBMT-sMF during training and placebo during detraining, placebo during training and PBMT-sMF during detraining or placebo throughout. All participants completed 12 weeks of unilateral resistance training (leg press and leg extension, twice weekly), followed by 4 weeks of detraining. PBMT-sMF or placebo was applied bilaterally to the anterior thigh prior to each session of exercise and two times per week during detraining. Outcomes included maximal voluntary contraction (MVC, primary outcome), as well as one-repetition maximum (1RM), muscle volume and anatomical cross-sectional area, measured at baseline and weeks 4, 8, 12 and 16. Results: PBMT-sMF significantly preserved muscle strength (MVC and 1RM) and structural features (volume and anatomical cross-sectional area) during detraining compared with placebo (p<0.05). The group that received PBMT-sMF during both the training and detraining phases demonstrated the greatest preservation across all outcomes. Conclusion: PBMT-sMF significantly attenuated strength loss and structural muscle changes during the detraining period after a resistance training programme. Trial registration number: NCT03858179.