When exercise goes awry: exertional rhabdomyolysis.

Exertional rhabdomyolysis occurs when exercise, often of the eccentric type, damages myofibrils and sarcolemma, with release of the enzyme creatine kinase and pigmented myoglobin into the serum. Severe muscle soreness and dark urine are the hallmark symptoms, and renal failure may develop. Formerly a disease of military recruits, it is now seen more often in exercisers. Although a genetic trait may predispose, the illness probably can be avoided by common sense behavior such as a gradual increase in exercise intensity, proper hydration before, during, and after exercise, and avoiding exercise in extremely hot or humid environments.