Effect of Low-level Laser Therapy on Exercise-induced Muscle Damage

Introduction: The effects of Low Level Laser Therapy (LLLT) on exercise-induced muscular damage have been studied over the last years. Studies have been conducted on animals and humans in order to try to show the benefits of the intervention, but there is still conflicting evidence about its protective and therapeutic effects.

Objectives: To describe the effects of LLLT on pain, strength and muscular inflammation after plyometric exercise.

Methods: A randomized, double-blinded, placebo-controlled trial with participation of 20 male healthy volunteers will be performed. Healthy and physically active individuals, aged between 18 and 35 years, with no history of injury on the lower limbs or contra-indications to maximal exercise performance will be included. A protocol of 10 series with 10 repetitions of the countermovement jump will be used to induce muscle damage at the lower limbs. Immediately before or after the exercise protocol, LLLT will be applied on one lower limb, while the other will receive placebo treatment. Phototherapy will be applied with an equipment of 810nm and a cluster with 5 diodes on 8 different points of the knee extensor muscle, totalizing a dosage of 240J. The placebo treatment will be held on the same way, but the equipment will be turned off. The volunteers will be evaluated at baseline (before the exercise protocol) and at follow-up of 24, 48 and 72 hours. The following outcomes will be evaluated: knee extensors isometric peak torque by Isokinetic Dynamometer, pain by Visual Analogue Scale and muscular tissue echo intensity by Ultrasonography.