Background: Photobiomodulation with low-level laser therapy (LLLT) has been widely used in clinical practice for diverse purposes, such as modulation of the inflammatory process, acceleration of the tissue repair process, pain relief and the enhancement of post-exercise recovery. Studies have demonstrated a beneficial interaction between photobiomodulation and the production of creatine kinase, with a reduction in the release of this marker of muscle damage when laser and/or LEDs is administered prior to high-intensity physical activity. The aim of the proposed study is to determine the influence of pre-exercise phototherapy on post-exercise muscle recovery.

Methods: A randomized, cross-over, sham-controlled, double-blind, clinical trial is proposed. The participants will be healthy professional soccer players aged 15 to 20 years from the same team with a body mass index within the ideal range (20 to 25 kg/m2) and no history of lower limb musculoskeletal injuries or surgery or back surgery in the previous six months. The athletes will be allocated to two groups based on the previously calculated sample size and will be blinded to allocation. Creatine kinase will be measured and the subjective perception of fatigue will be determined for each participant. The volunteers will then be randomly allocated to Group A, which will receive active phototherapy, and Group B, which will receive sham phototherapy. The athletes will undergo reevaluations immediately after as well as 48 hours after a football match. The data will be submitted to statistical analysis and the level of significance will be set to 5%.

Inclusion Criteria:

• Healthy professional soccer players aged 15 to 20 years from the same team with a body mass index in the ideal range (20 to 25 kg/m2) will be included in the study.

Exclusion Criteria:

• A history of musculoskeletal injuries and/or surgeries in the lower limbs or back surgery in the previous six months