Literature Review Delayed-onset muscle soreness (DOMS), or what is commonly referred to as postexercise muscle soreness, is the sensation of muscle discomfort and pain (Lieber & Friden, 2002 ) which is caused by vigorous and unusual resistance training or any form of muscular strain (Kisner & Colby, 2012). Other commonly observed symptoms are loss of strength and range of motion (ROM) (Valle et.at. 2013). These DOMS symptoms usually start to be felt about 12-24 hours after exercise and usually last a couple of days, but have been known to last 10-14 days. There has been a lot of research into various aspects of DOMS, from what causes it, how to prevent it, and how to treat it once it occurs in an athlete. But unfortunately very little is known about DOMS. In this section we will examine many aspects of DOMS. First, we will introduce the etiology of DOMS and the numerous theories as to why and how it occurs. Secondly, measures taken to prevent DOMS will be discussed. Finally, there have been many different approaches to treating an athlete with DOMS, and most of the actual benefits of these treatments are inconclusive at best, if not in some cases harmful. Possible Causes of DOMS Muscle Spasm TheoryOne theory that was thought to be the cause of DOMS in the 1960s was the muscle spasm theory. This theory suggests that a pain feedback loop caused by ischemia and the accumulation of metabolic waste products during exercise leads to muscle spasm (Kisner & Colby, 2012). It was hypothesized that the accumulation of these metabolic wastes caused the symptoms of DOMS and an ongoing pain-spasm reflex cycle that could last for many days thereafter (Vries, 1966). This theory has since been exposed to myofibrillar damage in human muscles affected by DOMS: an ultrastructural and immunoelectronic microscopic study. Histochemistry and Cell Biology, 121(3), 219-227. Ayles, S., Graven-Nielsen, T., & Gibson, W. (2011). Vibration-induced afferent activity increases delayed-onset muscle allodynia. The Journal of Pain, 12(8), 884-891.Vries, H. A. (1966). Quantitative electromyographic investigation of the spasm theory of muscle pain. American Journal of Physical Medicine & Rehabilitation, 45(3).Abraham, W. M. (1977). Factors of delayed muscle soreness. Medicine and Science in Sport and Exercise, 9(1), 11???20.Jakeman, J.R., Byrne, C., & Eston, R.G. (2010). Effectiveness of lower extremity compression and combined treatment of manual massage and lower extremity compression on symptoms of exercise-induced muscle damage in women. Journal of Strength and Conditioning Research, 24(11), 3157-3165.