In last years it has been demonstrated that photobiomodulation therapy (PBMT) has ergogenic effects. However some key aspects, such as the potentially beneficial effects of PBMT during the detraining period still remain unknown.

Therefore, the aim of this project is to evaluate the effects of PBMT applied before and after aerobic training sessions and during the detraining period.

It will be carried out a randomized, triple-blind, placebo-controlled trial.

Seventy-two volunteers will be randomly allocated to four experimental groups:

1. PBMT before and after the aerobic training sessions and PBMT during the detraining period;
2. PBMT before and after the aerobic training sessions and placebo during the detraining period;
3. Placebo before and after the aerobic training sessions and PBMT during the detraining period;
4. Placebo before and after the aerobic training sessions and placebo during the detraining period .

The individuals randomly allocated to the different groups will be subjected to 12 consecutive weeks of aerobic training performed on a treadmill 3 times a week on non-consecutive days. Each training session will last 30 minutes, with an intensity ranging from 85 to 90% maximum heart rate. PBMT or placebo will be applied before and after each training session. After the 12-week training period, the volunteers will receive the application of PBMT or placebo depending on the group to which they are allocated for 4 weeks (3 times a week) without training.

The data will be collected by a blind assessor. It will be analyzed time of the exercise (time until exhaustion), maximum oxygen consumption in absolute and relative values in relation to body mass (VO2max). Moreover, it will be evaluated the body composition. The evaluations will be performed before starting the protocol (baseline) and after 4, 8, and 12 weeks of training. They will also be performed after 4 weeks without training (detraining period).

The findings will be tested for their normality using the Shapiro-Wilk test. Parametric data will be expressed as mean and standard deviation and nonparametric data as median and respective upper and lower limits. Parametric data will be analyzed by two-way repeated measures analysis of variance (ANOVA; time versus experimental group) with post-hoc Bonferroni correction. Non-parametric data will be analyzed using the Friedman test and, secondarily, the Wilcoxon signed-rank test. Data will be analyzed in terms of both their absolute values and their relationship to the percentage change based on the values established in the baseline tests. The significance level will be set at p<0.05.

Inclusion Criteria:

• Healthy men;
• Aged from 18 to 35 years;
• Complete at least 80% of the study procedures will be included in the study.

Exclusion Criteria:

• History of musculoskeletal injury in the hip and knee regions in the 2 months before the study;
• Become injured during the study;
• Regularly use pharmacological agents and/ or nutritional supplements;
• Signs and symptoms of any neurological, metabolic, inflammatory, pulmonary, oncological, or cardiovascular disease that may limit the execution of high-intensity exercises.

Data will be shared upon request addressed to the principal investigator.

A researcher will program the device (placebo or PMBT) and will be instructed not to inform the volunteers or other researchers as to the type of treatment (PMBT or placebo). Therefore, the researcher responsible for the treatment will be blinded to the type of treatment being administered to the volunteers. The sounds and signals emitted from the device as well as the information displayed on the screen will be identical, regardless of the type of treatment (placebo or PBMT).