OBJECTIVE: To investigate the effects of photobiomodulation therapy (PBMT) on resistance training volume and discomfort of well-trained adults. BACKGROUND: PBMT has been used to attenuate fatigue in several physical exercise topics. However, it is unclear if PBMT can increase volume and reduce discomfort in resistance training well-trained individuals. METHODS: Fourteen participants (women = 7, 27.7 +/- 6.0 years and men = 7, 28.3 +/- 5.7 years) visited the laboratory three times, 7 days apart. In the first visit, 12-repetition maximum (12-RM) test was performed unilaterally on the standing calf raise machine. In the second and third visits, subjects were randomly submitted to a PBMT (60 J per site, 6 sites per limb, total dose = 360 J) or placebo treatment on the gastrocnemius and soleus muscles with a randomized crossover design. Five minutes after the treatment, subjects began the resistance training session, performed unilaterally with six sets of repetitions to concentric failure. In addition, the rate of perceived exertion for discomfort (RPE-D) was asked after each set. RESULTS: After the training session, it was observed a similar force reduction of 10.0 +/- 13.6% for placebo and 7.7 +/- 7.3% for PBMT (p = 0.815). No differences between PBMT and placebo was observed for the repetitions fatigue index (53.4 +/- 11.7% and 50.0 +/- 11.6%; p = 0.325) and total repetitions volume (55.4 +/- 10.9 and 54.8 +/- 13.0 reps; p = 0.764), respectively. RPE-D presented large means for all sets representing a large discomfort during resistance training to concentric failure for both PBMT (7.3 +/- 2.3) and placebo (7.5 +/- 2.5). CONCLUSIONS: The PBMT was not effective for increasing volume and reducing discomfort during resistance training performed to concentric failure by well-trained men and women.

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