Recovery from exercise-induced muscle fatigue is crucial for optimizing athletic performance, as maintaining appropriate functional capacity helps prevent injuries. Low-level laser therapy (LLLT) has shown potential benefits in muscle tissue recovery. However, its immediate and short-term effects on functional performance remain largely unexplored.

This study aimed to evaluate the immediate and short-term effects of LLLT on the functional performance of athletes experiencing exercise-induced muscle fatigue.

This study is a double-blind, randomized, placebo-controlled clinical trial. A total of 24 athletes were included based on the following criteria: they were handball or volleyball players, aged 18 to 35 years, with a consistent training routine of at least two sessions per week. Participants were randomly assigned to either the Intervention Group (IG, n = 12) or the Control Group (CG, n = 12). The study involved a daily fatigue protocol targeting the quadriceps muscles, consisting of 30 repetitions of jump squats, followed by either laser therapy or a placebo treatment for five consecutive days. The physiotherapist administering the laser therapy and the evaluator assessing the outcomes were both blinded to the participants' group assignments. Functional performance was assessed using the horizontal jump test, immediately after the laser or placebo therapy, using a modified hop test. Immediate effects and short-term effects were evaluated by comparing functional performance between groups after laser therapy or a placebo treatment on the first and fifth day, respectively.

No significant differences were observed between groups regarding the immediate or short-term effects of LLLT on functional performance [p = 0.099, 95% CI (130 ± 34.2 to 146 ± 32.0)]; [p = 0.996, 95% CI (145 ± 31.9 to 165 ± 37.3)], respectively.

This study found that LLLT, when applied immediately after exercise-induced muscle fatigue and over five consecutive days, did not significantly improve functional performance compared to placebo.

In this study, LLLT was applied post-fatigue based on the hypothesis that it could enhance functional performance. However, the findings do not support this premise, as current evidence remains insufficient to confirm that immediate post-fatigue LLLT application enhances functional outcomes. Further research is needed to establish its efficacy in this context.