en <div style=text-align: justify;><strong>Aims</strong>: Matrix Metalloproteinases (MMPs) are a group of in charge of extracellular matrix decomposition<span dir=RTL>.</span> The present research aimed at investigating the effects of 8 weeks of aerobic training on MMP plasma levels in lifeguards.<br> <strong>Materials & Methods:</strong> This study was a quasi-experimental one with 19 volunteer participants who were randomly assigned to either the control group (n=8) or the experimental group (n=11). The latter did aerobic exercises in water for 8 weeks at 65 to 75% of their reserved heart rate. Fasting blood samples (10cc) were collected from the brachial vein before and after the training protocol. <gwmw class=ginger-module-highlighter-mistake-type-1 id=gwmw-15548924597047660697780>was</gwmw> determined by applying ELIZA (Enzyme-Linked Immunosorbent Assay) method and the data were analyzed using SPSS 16 software. The significance level was set at p<0.05.<br> <strong>Findings</strong>: Results showed a significant increase in MMP-2 level in the experimental group as compared to the control group.<br> <strong>Conclusion</strong>: Increasing MMP levels due to 8 weeks of aerobic exercise in water may play an important role in physiological functions and tissue homeostasis. It may indicate remodeling of muscle fibers and connective tissue.<br> </div> Exercise, Matrix Metalloproteinase, Pilot Study 59 63 http://hehp.modares.ac.ir/browse.php?a_code=A-5-23982-1&slc_lang=en&sid=4 A. Rashid-lamir rashidlamir@um.ac.ir 1003194753284600117349 1003194753284600117349 Yes Exercise Physiology Department, Sport Sciences Faculty, Ferdowsi University of Mashhad, Mashhad, Iran R. Fazolahzade-Mousavi 1003194753284600117350 1003194753284600117350 No Physical Education Department, Neyshabour Branch, Islamtic Azad University, Neyshabour, Iran Gh.R. Mohammad Rahimi 1003194753284600117351 1003194753284600117351 No Exercise Physiology Department, Sport Sciences Faculty, Ferdowsi University of Mashhad, Mashhad, Iran