Introduction: Recent studies have shown positive results from the application of phototherapy for the improvement of performance and acceleration of the recovery process both in the application before and after exercise. However, the effects of phototherapy during combined training and after a primary adaptation process remain unclear.~Research objectives: The primary objective of the study is to analyze and compare the effects of phototherapy using different light sources (laser and LEDs) interacting with combined training on clinical, functional, and psychological outcomes and vascular endothelial growth factor. The secondary objective is to compare the benefits provided by phototherapy in participants with different levels of training adaptation.~Design: A controlled trial, double-blind, placebo-controlled will be conducted with stratified randomization and concealed allocation.~Participants and Setting: After fulfilling the eligibility criteria, forty-five male participants will participate in the study. The inclusion criteria include: healthy male, aged between 18-30 years who agree to participate in the study. Participants with the following will be excluded from the study: presence of anemia, inflammation, diabetes, history of metastasis or muscle injury in the lower limbs or spine in the previous six months, and occurrence of musculoskeletal injury during the study.~Procedure: In phase 1, the participants will perform six-weeks of combined training (sprints and squats). In phase 2, participants will be allocated, through stratified randomization (based on adaptation capacity to training), into three groups: active phototherapy group (AG), placebo phototherapy group (PG), and control group (CG). A new six-week training period will then start. In this phase the participants will carry out training normally with the adjusted loads and between sprints and squats will receive the recovery strategy related to the group to which they belong.~Intervention: Active and placebo phototherapy will be applied by a trained therapist, between sprints and squats, bilaterally to six sites of the quadriceps in direct contact with the skin. The dosage applied will be 30J per site. The same procedures as the AG will be applied to the PG, however the emitter will be disabled. During the period of recovery strategies for the AG and PG, the CG participants will remain seated for passive recovery, supervised by an independent therapist.~Measurements: The measurements include clinical (muscle soreness, pain threshold, perception of exertion, and perception of recovery), functional (squat strength and power, maximal voluntary isometric contraction, maximal incremental test, squat jump, and sprint test), and psychological (self-assessments of readiness for exercise, fatigue, vigor, pain, and belief of intervention effectiveness) outcomes and vascular endothelial growth factor.~Analysis: For analysis of functional outcomes, data normality will be checked by the Kolmogorov-Smirnov test with changes from baseline followed by the Student T test for comparisons. For other outcomes, sphericity of the data will be tested by the Mauchly's test. In case of violation of the sphericity assumption, Greenhouse-Geisser corrections will be used. Data will be analyzed using repeated-measures analysis of variance (Bonferroni's test will be performed when required), which provide information on time, group, and interaction effects. A significance level of 5% will be assumed for all statistical analysis.
Introduction: Recent studies have shown positive results from the application of phototherapy for the improvement of performance and acceleration of the recovery process both in the application before and after exercise. However, the effects of phototherapy during combined training and after a primary adaptation process remain unclear.~Research objectives: The primary objective of the study is to analyze and compare the effects of phototherapy using different light sources (laser and light emmiting diode - LED) interacting with combined training on clinical, functional, and psychological outcomes and vascular endothelial growth factor. The secondary objective is to compare the benefits provided by phototherapy in participants with different levels of training adaptation.~Design: A controlled trial, double-blind, placebo-controlled will be conducted with stratified randomization and concealed allocation.~Participants and Setting: After fulfilling the eligibility criteria, forty-five male participants will participate in the study.~Procedure: In phase 1, the participants will perform six-weeks of combined training (sprints and squats). In phase 2, participants will be allocated, through stratified randomization (based on adaptation capacity to training), into three groups: active phototherapy group (AG), placebo phototherapy group (PG), and control group (CG). A new six-week training period will then start. In this phase the participants will carry out training normally with the adjusted loads and between sprints and squats will receive the recovery strategy related to the group to which they belong.~Intervention: Active and placebo phototherapy will be applied by a trained therapist, between sprints and squats. During the period of recovery strategies for the AG and PG, the CG participants will remain seated for passive recovery, supervised by an independent therapist.~Measurements: The measurements include clinical, functional, and psychological outcomes and vascular endothelial growth factor.