DELAYED MUSCLE SORENESS - THE INFLAMMATORY RESPONSE TO MUSCLE INJURY AND ITS CLINICAL IMPLICATIONS

Delayed onset muscle soreness (DOMS) is a sensation of discomfort that occurs 1 to 2 days after exercise. The soreness has been reported to be most evident at the muscle/tendon junction initially, and then spre ading throughout the muscle. The muscle activity which causes the most soreness and injury to the muscle is eccentric activity. The injury t o the muscle has been well described but the mechanism underlying the injury is not fully understood, Some recent studies have focused on th e role of the cytoskeleton and its contribution to the sarcomere injur y. Although little has been confirmed regarding the mechanisms involve d in the production of delayed muscle soreness, it has been suggested that the soreness may occur as a result of mechanical factors or it ma y be biochemical in nature. To date, there appears to be no relationsh ip between the development of soreness and the loss of muscle strength , in that the timing of the two events is different. Loss of muscle fo rce has been observed immediately after the exercise, However, by coll ecting data at more frequent intervals a second loss of force has been reported in mice 1 to 3 days post-exercise. Future studies with human s may find this second loss of force to be related to DOMS. The role o f inflammation during exercise-induced muscle injury has not been clea rly defined. It is possible that the inflammatory response may be resp onsible for initiating, amplifying, and/or resolving skeletal muscle i njury. Evidence from the literature of the involvement of cytokines, c omplement, neutrophils, monocytes and macrophages in the acute phase r esponse are presented in this review. Clinically, DOMS is a common but self-limiting condition that usually requires no treatment. Most exer cise enthusiasts are familiar with its symptoms. However, where a musc le has been immobilised or debilitated, it is not known how that muscl e will respond to exercise, especially eccentric activity.