Risk of medical events in a supervised health and fitness facility.Med. Sci. Sports Exerc.,Vol. 31, No. 9, pp. 1233-1236, 1999.Purpose:This prospective epidemiological study examined the incidence of medical events during participation in a supervised health and fitness facility at a major medical center.Methods:Participants consisted of 7725 members of a corporate health and fitness program. Risk was defined by number of medical incidents per total number of event episodes multiplied by the average time of activity per episode (1000 participant-hours).Results:The first 2.5 yr of surveillance revealed 15 reported medically significant events (.048 per 1000 participant-hours). There were two medical emergencies yielding a rate of .0063 per 1000 participant-hours.Conclusion:The results of this study support the position that the expected health benefits of participation in a physical activity program at a supervised health and fitness facility outweigh the risks of such participation.