The effects of phototherapy has been widely studied by some research groups. The investigators know that there are positive results with light application to improve muscle performance and delay fatigue. However, there are few studies showing its´ effects on muscular training. Therefore, the aim of this study was to assess the effects of phototherapy applied at different times during 12 weeks of strength training. For such, 48 volunteers, healthy male, from 18 to 35 years old were recruited to perform a strength training protocol for the anterior muscle of the thigh development. Volunteers performed the training protocol twice a week for 12 weeks. There were assessed isometric peak torque in isokinetic dynamometer, 1-repetition maximum test in the leg extension and leg press machines and bilateral thigh perimetry.

This is a clinical, randomized, controlled placebo and double-blind study. Forty-eight participants performed strength training protocol. Subjects practiced a protocol training with 80% of the load, measured through 1-repetition maximum test. The training protocol consisted in performing 5 sets of 10 repetitions, twice a week, employing leg extension and leg press machines.

Phototherapy, active or placebo, were applied in 6 different points of anterior muscle of the thigh before and after each training session. Only one investigator, that did not participate in any phase of the assessments and trainings sessions, knew about what program is active or placebo in phototherapy device. Randomisation carried out by a simple drawing of lots (A, B, C, or D) in the first visit. The phototherapy unit emitted the same sound regardless of the program used, active or placebo. Either strength training lasted 12 weeks and assessments were performed at baseline, 4, 8 and 12 weeks. There were evaluated maximal voluntary contraction (MVC), bilateral thigh perimetry and 1-repetition maximum test (1-RM).

Inclusion Criteria:

There were included in the study

• healthy individuals,
• active,
• aged between 18 and 35 years old,
• male,
• presenting no history of musculoskeletal injury in the regions of the hip and knee in the two months prior to the study.
• that are not making use of pharmacological agents and / or nutritional supplements, and
• that have at least 80% of attendance to training.

Exclusion Criteria:

The participants were excluded if they

• present some musculoskeletal injury during the study