RESUMEN
BACKGROUND: Photobiomodulation (PBM) improves motor performance despite doubts whether it occurs immediately or late after a single dose. We evaluated the effect of a cluster PMB (laser + LED) single dose on muscle fatigue recovery in young sedentary adults, both immediately and in the short term (period between 24 and 48 h) after the fatiguing event. METHODS: Randomized clinical trial with 60 volunteers randomized in 5 groups (n = 12 in each): control/(CG); placebo/(SG); PBM in knee extensor/(KE_G); plantar-flexor/(PF_G); knee extensor + plantar-flexor/(KE + FP_G). Before the intervention (pre) a fatiguing event (FE) was applied, which consisted in going up and down one step until exhaustion. Repetition number (RN) and time to exhaustion (TTE) were recorded. Then each group received its respective intervention and immediately after that, the FE was performed again (immediate post). In the period between 24 and 48 h after irradiation, a new FE was performed (late post). In addition to the comparative statistics, complementary metrics (if the mean difference [Diff] between the comparison pairs was higher or lower than minimum detectable change [MDC] and effect size [ES]) were calculated. RESULTS: Through the integrated analysis of inferential statistics and complementary metrics, it was observed that although there was no time of evaluation effect, there was a group effect. PBM improved performance in KE + FP_G (p-value<0.05; Diff>MDC; ES = moderate) and PF_G (p-value>0.05; but Diff > MDC; ES = moderate) regarding CG for both RN and TTE. CONCLUSION: A PBM single dose irradiation may improve motor performance and there is specificity of the irradiated muscle group, although it does not depend on the moment.