Time Response of Photobiomodulation Therapy on Muscular Fatigue in Humans.

Rossato, M, Dellagrana, RA, Sakugawa, RL, Lazzari, CD, Baroni, BM, and Diefenthaeler, F. Time response of photobiomodulation therapy on muscular fatigue in humans. J Strength Cond Res 32(11): 3285-3293, 2018-The aim of this study was to identify the effects of 2 different time responses on fatigue of knee extensor. Sixteen male volunteers (26 ± 6.0 years, 81 ± 12 kg, and 181 ± 7.4 cm) participated in the study. Participants performed the same protocol in 5 sessions {control, placebo (placebo applied both 6 hours before and immediately before the test), 6 hours before + immediately before (photobiomodulation therapy [PBMT] applied both 6 hours before and immediately before the test), 6 hours before (PBMT applied 6 hours before and placebo applied immediately before the test), and immediately before (placebo applied 6 hours before and PBMT applied immediately before the test)}. Photobiomodulation therapy was applied on knee extensor (9 sites; 30 J per site). Maximal isometric voluntary contraction (MIVC) was assessed before and after an isokinetic fatigue (45 flexion-extension concentric at 180°·s), associated with electromyography (root mean square [RMS] and median of frequency [MF]). For MIVC, there was no treatment × time interaction for all variables. Time effect was observed for peak torque (PT), RMS, and MF. Treatment effect was verified for PT, and 6 hours before + immediately before condition presented higher PT during MIVCpre than control (p = 0.004) and placebo (p = 0.044). The immediately before presented higher PT values than control (p = 0.047). Regarding MIVCpost, the PT for 6 hours before + immediately before presented higher values than control (p = 0.001) and placebo (p = 0.004). Peak torque during MIVC (pre to post) was reduced in 6 hours before + immediately before treatment (26%) compared with control (33%), placebo (29%), and immediately before (32%). The application of PBMT 6 hours + immediately before and immediately before exercise protocol is able to reduce the fatigue.