Delayed muscle onset soreness (DOMS) is a well-known consequence of many forms of muscular activity. DOMS is a delayed reaction to exercise, typically not experienced or observed for 12 hours or longer after a particular athletic event.
DOMS is characterized by acute soreness in the muscles, often in conjunction with localized swelling. The most common type of DOMS is experienced when the athlete has participated vigorously in a new or an unaccustomed activity, for instance, the athlete participates in a 15-mi (25 km) run where the longest distance previously covered was 5 mi (8 km). DOMS is a part of the natural adaptive processes of the body to the new muscles stress to which the musculoskeletal system has been subjected. DOMS is most common when the activity requires the muscles to perform an eccentric contraction, where the muscles are subjected to a nervous system impulse to produce movement while the muscle is being extended away from the body. Running downhill, the delivery of a boxing punch, and movements such as pushups are classic examples of eccentric contractions. An unfamiliar eccentric contraction often produces a micro-tearing of the muscle fiber, which is the cause of both the subsequent pain and the related swelling.
DOMS must be contrasted with other manifestations of muscle pain that occur as a result of exercise. Muscles that are sore immediately during or after an activity are typically the subject of simple muscle fatigue, often more pronounced due to the inability of the body to efficiently remove waste products generated as a part of cellular energy production from the muscle; lactate is an example of waste. Muscle cramps also have a separate cause from that of DOMS, and result of reduced fluid levels and a corresponding disruption in the optimal level of lectrolytes—particularly sodium—within the body. Reduced levels of sodium impair the ability of nerve impulses to be transmitted into the muscle to regulate the firing of the appropriate neuron that provides the muscle fibers with the command to contract. This condition is readily corrected by rest and an infusion of fluids and electrolytes.
In addition to the requisite degree of caution that an athlete should observe in the attempt at a new and strenuous exercise without appropriate conditioning, the risk of DOMS can be reduced through the implementation of a focused warm-up and cool-down regime. DOMS may persist for a period of days after its onset; exercise of the non-affected areas will help the athlete preserve a better level of fitness while the DOMS-afflicted muscles heal, as will gentle manipulation of the muscles through stretching and massage.