A randomized, double-blind, placebo-controlled clinical trial was performed at the Laboratory of Phototherapy in Sport and Exercise at Nove de Julho University in the city of São Paulo, Brazil.
Fifty healthy untrained male subjects were recruited from university staff and students to participate in the study. All participants voluntarily must agree to participate and they signed the informed consent statement. The intention-to-treat analysis was followed.
The volunteers were randomly allocated to five experimental groups (n=10 per group) according to the applied comparator. Randomisation was carried out by a simple drawing of lots (A, B, C, D or E). Blood samples (10 ml) was taken by a qualified nurse to analyse CK activity posteriorly. This blood collection was repeated 1 minute, 1 hour, 24, 48, 72 and 96 hours after eccentric protocol.
A visual analogue scale (VAS) of 100 mm was used as a self-rating of volunteers DOMS intensity, with assistance of a blinded researcher. DOMS assessments were performed at baseline, immediately after eccentric exercise protocol (1 minute), and it was repeated at 1, 24, 48, 72 and 96 hours after the exercise protocol. Before exercise protocol, volunteers will perform a stretching and warm-up of the non-dominant lower limb and then they will perform Maximum voluntary contraction (MVC) to evaluate muscle function. MVC measurements were repeated at the same time intervals as the CK measures.
The exercise protocol consists in 75 eccentric isokinetic contractions of the knee extensor musculature in the non-dominant leg (5 sets of 15 repetitions, 30-second rest interval between sets) at a velocity of 60°.seg-1 in both the eccentric and concentric movements with a 60° range of motion (between 90° and 30° of knee flexion).
Regarding to treatment, all volunteers received the treatment according to randomisation three minutes after eccentric exercise protocol. Comparators were repeated at 24, 48, and 72 hours following the collection of additional blood samples for CK analyses and MVC and DOMS assessments.
The five groups was divided in: PBMT (photobiomodulation therapy)+cryotherapy; cryotherapy+PBMT; active PBMT; placebo PBMT and only cryotherapy.
PBMT was applied employing a cordless, portable GameDay™ Super Pulsed Laser (manufactured by Multi Radiance Medical, USA) to 6 sites of quadriceps femoris in direct contact with the skin (2 centrally - rectus femoral and vastus intermedius; 2 laterally - vastus lateralis; and 2 medially - vastus medialis) and cryotherapy was done with two flexible ice packs filled with ice cubes and water (with a volume of 1.15 liters each) that will cover the entire quadriceps for 20 minutes.
