Low-level phototherapy to improve exercise capacity and muscle performance: a systematic review and meta-analysis

The aim of this study was to evaluate the effectiveness of pre-exercise low-level phototherapy (Light-Emitting Diode therapy [LEDtherapy] or Light Amplification by Stimulate Emission of Radiation therapy [LASERtherapy]) in increasing exercise capacity and muscle performance of people undergoing exercise when compared to placebo treatment. Randomized controlled trials and crossover studies were sought on CENTRAL, MEDLINE, EMBASE, SciELO, PEDro and LILACS from its inception up to February 2015. References lists of included studies were sought for additional relevant research. Two authors independently extracted data on study design, treatment parameters, exercise capacity (number of repetitions, time to exhaustion, blood lactate concentration and lactate dehydrogenase activity) and muscle performance (torque, power and strength) using an structured table. Agreement should be reached by consensus or by a third reviewer. Sixteen studies involving 297 participants were included. Improvement of number of repetitions (mean difference [MD] [95 % confidence interval] = 3.51 repetitions [0.65–6.37]; P = 0.02), delay in time to exhaustion (MD = 4.01 s [2.10–5.91]; P < 0.0001), reduction in lactate levels (MD = 0.34 mmol/L [0.19–0.48]; P < 0.00001) and increased peak torque (MD = 21.51 Nm [10.01–33.01]; P < 0.00001) were observed when LASERtherapy was applied. LEDtherapy meta-analyses were performed with two studies and retrieved no between-group statistically significant difference in power, lactate levels or time to exhaustion. Although our results suggest that LASERtherapy is effective in improving skeletal muscle exercise capacity, the quality of the current evidence is limited.