Researches have been performed to investigate the effects of phototherapy on improving performance and reduction of muscular fatigue. However, a great variability in the light parameters and protocols of the trials are a concern to establish the efficacy of this therapy to be used in sports or clinic. The aim of this study is to investigate the effectiveness, moment of application of phototherapy within an exercise protocol, and which are the parameters optimally effective for the improvement of muscular performance and the reduction of muscular fatigue in healthy people. Systematic searches of PubMed, PEDro, Cochrane Library, EMBASE, and Web of Science databases were conducted for randomized clinical trials to March 2017. Analyses of risk of bias and quality of evidence of the included trials were performed, and authors were contacted to obtain any missing or unclear information. We included 39 trials (861 participants). Data were reported descriptively through tables, and 28 trials were included in meta-analysis comparing outcomes to placebo. Meta-analysis was performed for the variables: time until reach exhaustion, number of repetitions, isometric peak torque, and blood lactate levels showing a very low to moderate quality of evidence and some effect in favor to phototherapy. Further investigation is required due the lack of methodological quality, small sample size, great variability of exercise protocols, and phototherapy parameters. In general, positive results were found using both low-level laser therapy and light-emitting diode therapy or combination of both in a wavelength range from 655 to 950 nm. Most of positive results were observed with an energy dose range from 20 to 60 J for small muscular groups and 60 to 300 J for large muscular groups and maximal power output of 200 mW per diode.
Keywords: Exercise; Fatigue; Light emitting diode; Low-level light therapy; Performance; Phototherapy.