Reduced peripheral resistance and other factors in marathon collapse.

Athletes sometimes collapse either during or after exercise. Conditions that cause collapse during exercise may be life-threatening and account for 10-15% of all exercise-related medical encounters at endurance sporting events. These conditions are not always 'sports-specific' and are managed according to the usual clinical care guidelines. The majority (>85%) of exercise-related collapse occurs after athletes have completed the event and key features are that patients are fully conscious and they have no clinical evidence for other serious medical conditions, but they have postural hypotension (blood pressure usually <100mm Hg) with unexpectedly low heart rates (<100 beats per minute). The cause of the postural hypotension appears to be the combination of physiological changes induced by exercise that tend to maintain a state of abnormally low peripheral vascular resistance for some hours after exercise. The most appropriate treatment for these patients is the supine position with the legs and pelvis above the level of the heart. Additional therapeutic interventions should be reserved for those who fail to respond adequately (blood pressure >100mm Hg; normal heart rate) to this simple treatment.