Crossfit® is a method of strength training and fitness built on functional movements, constantly varied and executed at high intensity. Competitions such as the Crossfit® involve physically demanding activities, which in addition to being performed at high intensity also use great measures of aerobic capacity related with performance. These characteristics cause metabolic and muscular stress, as well as a decrease in physical performance. The demand for intensity is the cause of concern regarding the practice of Crossfit® and the risk of injuries. Studies using photobiomodulation therapy combined with static magnetic fields (PBMT/sMF) to delay fatigue and increase performance have obtained positive results in different types of exercise and application times. However, there are no studies investigating the effects of PBMT/sMF in training with similar characteristics as Crossfit®. Therefore, the aim of this project is to verify the effects of PBMT/sMF on performance and muscle recovery of Crossfit® athletes at different times of application (pre workout of the day [WOD] and/or post WOD) in order to determine the best way to use the therapy.

To achieve the proposed objective it will be performed a randomized, crossover, triple-blind (volunteers, outcome assessors and therapists), placebo-controlled trial.

Twelve volunteers will be allocated to four interventions/situation. The order of the interventions/situations will be randomized.

The volunteers will be treated by a blinded therapist.

The outcomes will be obtained at baseline (prior to WOD), and 1 hour, 24 and 48 hours after WOD. Except for the ratings of perceived exertion that will be obtained at baseline, after WOD, and 1 hour, 24 and 48 hours after WOD. In addition, for the functional analysis the data will be collected at baseline, after applied intervention, and 1 hour, 24 and 48 hours after WOD. The data will be collected by a blinded assessor.

The WOD will be consisted in finish as quickly as possible a sequence of three exercises (Calories in Assault AirBike®, Hang Squat Clean and Box Jump Over), in a well-known series model for the athletes, without rest.

The investigators will analyze: ratings of perceived exertion; activity of creatine kinase (CK); levels of the cytokine Interleukin-6 (IL-6), and maximum number of free squat reps in 1 minute.

Statistical analysis:

All data will be analyzed both in their absolute values and in relation to their percentage variation from the values obtained in the pre-WOD (baseline) assessments. The results obtained will be tested for normality using the Kolmogorov-Smirnov test. If data show normal distribution, the ANOVA test (one or two way depending on the outcome analyzed) with post-hoc Bonferroni will be used. The level of statistical significance will be p<0.05.

Inclusion Criteria:

• Crossfit® amateur male athletes;
• who did not present a history of musculoskeletal injury in the regions of the hips, knees and calves in the month preceding the study;
• who were not using pharmacological agents;
• athletes should have been practicing the sport for at least 1 year;
• voluntarily commit to participate in all stages.

Exclusion Criteria:

• who presented musculoskeletal or joint injuries during data collection.

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).