The effects of sports and of other forms of recreation on health are largely unknown because available epidemiologic research techniques have not been applied. "Exposure" to risk, incidence and prevalence of injuries and benefits, and differences between injured and noninjured and participants and nonparticipants must be measured for causal inferences and preventive action. Variables and questions for study relate to the sport, participants, environment, audience, officials, equipment, medical care, late effects such as epilepsy and musculoskeletal pathology, time and place, and cultural functions of aggression and violence. The incompleteness of information should not, however, justify avoiding decisions, for example, in relation to the prevention of the continuing deaths of high school and other football players. Little evidence supports the "body-contact" cult. Research should provide information to minimize injuries and maximize benefits.
From the scientific standpoint, the effects of sports on health are largely unknown. Specific research has been scanty, and
Haddon W. Principles in Research on the Effects of Sports on Health. JAMA. 1966;197(11):885–888. doi:10.1001/jama.1966.03110110109024