Photobiomodulation before blood flow restriction exercises: a randomized clinical trial

This study investigate the effects of photobiomodulation therapy applied before exercises with blood flow restriction during low-load or high-load exercises on muscle adaptations, muscle damage, and redox status. Forty-five untrained men were randomly assigned to four groups: photobiomodulation therapy-blood flow restriction (30% of maximal isometric voluntary contraction), placebo-blood flow restriction (30% of maximal isometric voluntary contraction), photobiomodulation therapy-high-load exercise (80% of maximal isometric voluntary contraction), and placebo-high-load exercise (80% of maximal isometric voluntary contraction). Elbow flexion exercises were performed twice weekly for 8 weeks, followed by a 4-week detraining period. After 8 weeks, photobiomodulation therapy-blood flow restriction, photobiomodulation therapy-high-load exercises, and placebo-blood flow restriction groups significantly increased muscle strength (<i>p</i><0.05) with non-significant increases in the placebo-high-load exercise group. The photobiomodulation therapy-blood flow restriction group demonstrated a superior magnitude of effects compared to the placebo-high-load exercise (+10.2%) and placebo-blood flow restriction (+7%; <i>p</i><0.008) groups. Only the placebo-blood flow restriction group reduced the fatigue index post-intervention. During the detraining period, both blood flow restriction groups maintained superior muscle strength compared to baseline levels. The placebo-high-load exercise group exhibited higher creatine kinase activity post-exercise compared to the other groups. No significant changes were observed in nitric oxide, thiobarbituric acid reactive substances, carbonylated proteins, or total antioxidant capacity immediately post-exercise. However, the total antioxidant capacity levels were increased in all groups after 8 weeks of exercise and following a 4-week detraining period. Overall, the photobiomodulation therapy-blood flow restriction group promoted greater gains in muscle strength compared to the placebo-high-load exercise and placebo-blood flow restriction groups.