Myoglobinemia and endurance exercise: a study of twenty-five participants in a triathlon competition

Twenty-five athletes competing in a triathlon, an endurance competition, were studied to determine the relationship of sustained muscle exertion with myoglobinemia and clinical rhabdomyolysis. Of 24 athletes who completed the event, each individual demonstrated a dramatic rise and fall in serum myoglobin over a 24 hour period, with an average peak level of 842 ng/ml. While all subjects exhibited symptoms of myalgia after exertion, none required hospitalization. A significant correlation was demonstrated with average serum myoglobin and finishing time (P less than 0.0125) and postexercise temperature (P less than 0.05). Appropriate training of individuals, whether athletes or military recruits, appears to be an important factor in reducing myoglobinemia. Exercise-induced myoglobinemia appears to be dependent on intensity of athletic performance, measured as a function of time, distance, and activity performed. The athletes who finished first had the highest levels of myoglobinemia.