Introduction: Photobiomodulation therapy (PBMT) is based on the emission of light ranging from red to near-infrared spectra by different devices based on diode lasers or light-emitting diodes. These devices emitting different wavelengths can increase mitochondrial activity and energy synthesis (ATP - adenosine triphosphate) that in turn can help to prevent muscle damage, decrease muscle fatigue and enhance muscle performance. Thus, PBMT can be a promising therapeutic resource in the sports field. Objectives: The aim of this study is to verify the effect of PBMT on the muscle performance and prevention of muscle damage and delayed onset muscle soreness (DOMS) in professional soccer players submitted to a muscle damage protocol. Methodology: The present study is a randomized sham-controlled clinical trial following the CONSORT guidelines.

Participants will be allocated into 3 balanced randomized groups, as follows: 1) PBMT post muscle damage protocol (PBMT-post); 2) PBMT pre (PBMT-pre) and 3) PBMT placebo (PBMT-sham). All groups will be submitted to a) anamnesis; b) measurement of blood levels of creatine phosphokinase (CK); c) delayed onset muscle soreness (DOMS); d) muscle performance tests (Squat Jump test (SJ) and Counter Movement Jump (CMJ)); e) dynamometry of the knee extensor muscles. Whole body PBMT will be applied according to the groups, during 10 min (sham or effective), with an effective dose of 48.97 J/cm2 and irradiance of 81.62 mW/cm2. Muscle damage protocol will consist of 8 exercises for lower limb muscles, with 3 sets of 10 repetitions each, 1 minute of rest between sets, and 2 minutes of rest between exercises. Next, participants will be evaluated for levels of CK, DOMS and muscle performance (SJ, CMJ, dynamometry) at 24, 48 and 72 hours after muscle damage protocol. Data will be analyzed and compared between groups with a significance level of 5%.

Inclusion Criteria:

• Male individuals aged between 18 and 35 years, professional soccer players who engage in training at least 5 times a week, will be selected.

Data collection will be conducted at the Desportivo Brasil Football Club, located in Porto Feliz, São Paulo. The sample will consist of team members, with a total of 30 athletes established to compose the sample. All data collection will take place in the same location.

Exclusion Criteria:

• Individuals with any impediment to physical activity or those presenting dysfunctions that may impair the neuromuscular system will be excluded.

All participants were professional male soccer players (18-35 years) from the same training team.

Baseline demographic and anthropometric data were collected prior to randomization.

Adverse event data were collected over a period of 4 consecutive days, from baseline through 72 hours post-protocol.

Adverse events were monitored and recorded using standard definitions aligned with ClinicalTrials.gov. No deviation from the standard definitions of adverse event or serious adverse event occurred. Participants were systematically questioned and observed during all evaluation sessions across the 4-day study period.