Effect of Low-Level Laser Therapy on Muscle Strength and Endurance and Post-Exercise Recovery of Young Adult: A DoubleBlind, Placebo-Controlled, Randomized Clinical Trial

Background. Recovery or post-exercise rehabilitation is an essential part of exercise training. Low-level Laser Therapy (LLLT) is a modality increasing interest for recovery because of having a conservative and non-aggressive method. LLLT also decreases the production of fatigue-related biomechanical markers, such as lactate, C-reactive protein (CRP), and Creatine kinase (CK). Objectives. To investigate the effect of low-level laser therapy on muscle strength and endurance and post-exercise recovery of young adults between 20-35 years old. Methods. Fifty subjects were enrolled in this double-blind, placebo-controlled, randomized clinical trial study. Three days after the familiarization session, the subjects were divided into two groups via block randomization: the first group received pre-exercise laser at 810 nm, 60mW, and 60Hz frequency for 30 seconds on three point’s rectus femoris muscle. The other group received a placebo laser on the same points. The operator who was blinded to the allocation of the subjects applied the phototherapy. They underwent an exercise test with a treadmill and a maximum number of knee extensions with a 10 Kilograms (Kg) weight. The test results, level of blood lactate, perceived exertion of fatigue, and muscle soreness were assessed, and the results were analyzed. Results. The blood lactate level, the severity of muscle pain, the perceived exertion of fatigue, and the repetition of knee extensions with a 10 kg weight, had a statistically significant difference between laser and placebo groups (p < 0.05). Conclusion. The use of LLL before exercise may improve muscular performance and reduce muscle soreness and fatigue.