Light-emitting diodes (LED) therapy applied between two running time trials has a moderate effect on attenuating delayed onset muscle soreness but does not change recovery markers and running performance

Summary Purpose The study aimed to examine the recovery/performance effects of LED therapy applied between two running time trials on blood lactate, creatine kinase (CK), delayed onset muscle soreness (DOMS) and heart rate variability (HRV) in physically active participants. Methods Eleven healthy and young males (26.7 ± 4.8 years) volunteered to participate. Visits in the laboratory were divided into two phases (i.e., two different weeks with four visits each) using the same exercise protocols, but differing randomly in recovering intervention conditions: placebo (PLA) or LED therapy (LED). The minimal and maximal duration for each phase was one and two weeks. On the first day of each phase, the participants performed two (test 1 and test 2) time trials of 40-minute duration with six hours of interval separating the trials. Blood lactate, CK, DOMS, HRV were used as recovery measurements. Variables were compared using two-factor ANOVA for repeated measures followed by the Bonferroni post-hoc test for multiple comparisons. Cohen's effect size (ES) was used to estimate the magnitude of the difference. Results We found that LED therapy had a moderate ES on decreasing how much DOMS increased before test 2, despite no significant effect of LED therapy on CK, lactate concentrations, DOMS and parasympathetic activity (i.e., HRV). No influences were observed in endurance running performance (i.e., mean velocity in the 40-minute time trial). Results suggest LED therapy applied between two running time trials has a moderate effect on attenuating delayed onset muscle soreness but does not change recovery markers and running performance.