en حرکت‌شناسی و آسيب‌های ورزشی Kinesiology and Sport Injuries مقاله اصیل Original Article <div style="text-align: justify;"><strong>Background. </strong>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).<br> <strong>Objectives. </strong>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.<br> <strong>Methods. </strong>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&rsquo;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.<br> <strong>Results. </strong>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).<br> <strong>Conclusion. </strong>The use of LLL before exercise may improve muscular performance and reduce muscle soreness and fatigue.</div> Low-Level Laser Therapy (LLLT), Muscle Performance, Muscle Fatigue 0 0 http://aassjournal.com/browse.php?a_code=A-11-1396-1&slc_lang=en&sid=1 Amir Hosein Abedi Yekta abedy_yekta@yahoo.com 100319475328460010200 100319475328460010200 No Department of Sports Medicine, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran Faraj Tabeii tabeiefar@gmail.com 100319475328460010201 100319475328460010201 No Department of Nuclear Medicine, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran Shahin Salehi salehi2955@yahoo.com 100319475328460010202 100319475328460010202 No Department of Sports Medicine, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran Mohammad-Reza Sohrabi m.r.sohrabi@gmail.com 100319475328460010203 100319475328460010203 No Department of Community Medicine, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran Mehrshad Poursaeidesfahani mpoorsaid@yahoo.com 100319475328460010204 100319475328460010204 No Department of Sports Medicine, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran Mohammad Hassabi hassabi@yahoo.com 100319475328460010205 100319475328460010205 No Taleghani Hospital, Research Development committee, Department of Sports Medicine, Shahid Beheshti University of medical Sciences, Tehran, Iran Nina Hazegh h.anahita64@yahoo.com 100319475328460010206 100319475328460010206 Yes Department of Sports Medicine, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran Behnaz Mahdaviani behnaz_mahdaviani@yahoo.com 100319475328460010207 100319475328460010207 No Department of Sports Medicine, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran