Effects of Photobiomodulation Therapy in Strength Training and Detraining in Humans

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

Forty-eight volunteers will be randomly allocated to four experimental groups:

• PBMT before the strength training sessions and PBMT during the detraining period;
• PBMT before the strength training sessions and placebo during the detraining period;
• Placebo before the strength training sessions and PBMT during the detraining period;
• Placebo before the strength training sessions and placebo during the detraining period .

The individuals randomly allocated to the different groups will be subjected to 12 consecutive weeks of dynamic strength training involving leg-press and knee extension exercises in leg-press and leg-extension machines, respectively, 2 times a week.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 (2 times a week) without training.

The data will be collected by a blind assessor. It will be analyzed the muscular strength and the structural properties of quadriceps before starting the study (baseline), at 4, 8, and 12 weeks after starting the training period, and at 4 weeks after completing the training (detraining period), in both lower limbs.

The findings will be tested for their normality using the Shapiro-Wilk test. Parametric data will be expressed as mean and standard deviation and non-parametric 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.