Time Response of Photobiomodulation Therapy on Muscular Fatigue in Humans

Abstract

The aim of this study was to identify the effects of two different time responses on fatigue of knee extensor. Sixteen male volunteers (26±6.0 years 81±12 kg, and 181±7.4 cm) participated of study. Participants performed the same protocol in five sessions, [control, placebo (placebo applied both 6 hours before and immediately before the test), 6h before + immediately before (PBMT applied both 6 hours before and immediately before the test), 6h 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)]. PBMT was applied on knee extensor (9 sites; 30 J per site). Maximal isometric voluntary contraction (MIVC) were 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. While treatment effect was identified for MIVC, which the 6h before + immediately before presented higher PT pre than control (p=0.004) and placebo (p=0.044). The immediately before presented higher PT values than control (p=0.047). Regarding PT post, 6h before + immediately before presented higher values than control (p=0.001) and placebo (p=0.004). PT during MIVC (pre to post) was reduced in 6h before + immediately before treatment (26%) compared to control (33%), placebo (29%), and immediately before (32%). The application of PBMT 6h + immediately before and immediately before exercise protocol is able to reduce the fatigue.

What is the optimal time-response window for the use of photobiomodulation therapy combined with static magnetic field (PBMT-sMF) for the improvement of exercise performance and recovery, and for how long the effects last? A randomized, triple-blinded, placebo-controlled trial

“…Authors did not observe effects at 5 mins time-response window, but found increased muscular ATP and increased performance in mice when 3 h, 6 h and 24 h (1-day) time-response windows were used, with better results in favor of 6 h time-response window. Interestingly, the clinical outcomes observed both by Rossato et al [ 35 ] and by our findings did not corroborate with the outcomes observed by Ferraresi et al both in cultured myotubes (in vitro) [ 43 ] and mice (in vivo) [ 38 ]. Despite Ferraresi et al [ 38 ] state that “ Although the time response in mice and humans is not the same, athletes might consider applying LEDT at 6 h before competition .”, the outcomes from both randomized controlled trials performed with human volunteers showed that indeed the time-response window in mice and humans is not exactly the same.…”

“…Our outcomes agreed that PBMT-sMF is able to increase performance, however, with a single irradiation applied at 5 mins, 3 h or 6 h before a high intensity exercise protocol with decreased effects when PBMT-sMF is applied 1-day (24 h) before the exercise activity. We believe that the extensive optimization of parameters previously performed with the same PBMT-sMF technology used in our study [ 10 , 15 , 19 – 21 ], and the increased effects of the synergistic use of three wavelengths [ 3 ], besides the combination of PBMT with sMF [ 28 ], which allowed for only one treatment within 6 h to have positive effects instead two treatments (6 h and 5 mins before) as previously observed [ 35 ]. Thus, we believe that our study brings new knowledge to the existing evidence body in literature.…”

“…Authors did not observe effects at 5 mins time-response window, but found increased muscular ATP and increased performance in mice when 3 h, 6 h and 24 h (1-day) time-response windows were used, with better results in favor of 6 h time-response window. Interestingly, the clinical outcomes observed both by Rossato et al [35] and by our findings did not corroborate with the outcomes observed by Ferraresi et al both in cultured myotubes (in vitro) [43] and mice (in vivo) [38]. Continuous variables are expressed as mean (±SD) MVC Maximum Voluntary Contraction (time = p < 0.0001, group = p < 0.0001, interaction = p < 0.0001); CK Creatine Kinase (time = p < 0.0001, group = p < 0.0001, interaction = p < 0.0001); DOMS Delayed Onset Muscle Soreness (time = p < 0.0001, group = p < 0.0001, interaction = p < 0.0001) a p < 0.05 compared to control, aa p < 0.01 compared to control, aaa p < 0.001 compared to control, aaaa p < 0.0001 compared to control; bb p < 0.01 compared to placebo, bbb p < 0.001 compared to placebo, bbbb p < 0.0001 compared to placebo; cc p < 0.01 compared to PBMT-sMF 1-day, ccc p < 0.001 compared to PBMT-sMF 1-day, cccc p < 0.0001 compared to PBMT-sMF 1-day.…”

“…It is important to highlight that the only one previous randomized controlled trial [35] that has similar aims than ours, only investigated two time-response windows (5 min and/or 6 h), used a different dose than ours (270 J to the quadriceps), used isolated PBMT, and only investigated muscular performance aspects through isokinetic dynamometer and muscle activation through electromyography during and immediately after the exercise protocol. Rossato et al [35] observed that PBMT applied 6 h before plus immediately before a high-intensity exercise protocol was able to reduce the strength fall in healthy and physically active subjects. Our outcomes agreed that PBMT-sMF is able to increase performance, however, with a single irradiation applied at 5 mins, 3 h or 6 h before a high intensity exercise protocol with decreased effects when PBMT-sMF is applied 1-day (24 h) before the exercise activity.…”

“…However, the time-response window for the use of PBMT either isolated or combined with sMF (PBMT-sMF) before physical activity still was not fully investigated in clinical scenario, and there is much speculation and overstatements regarding this matter. In fact, the only other randomized controlled trial investigating the time-response window was limited by focusing on the immediate effects of two time-response windows of PBMT on muscle fatigue [ 35 ]. Additional research is needed to understand more time window responses and the multi-day effects on delayed onset muscle soreness and biochemical markers.…”