Sport and exercise as contributors to the health of nations.

Self-reported rates of participation in sport vary by country. In the UK, about 40% of men and women aged 16 years or older participate in at least one sport every week. Although few data exist to assess trends for participation in sport, there is little evidence of change in the past decade among adults. Large cohort studies suggest that such participation in sport is associated with a 20-40% reduction in all-cause mortality compared with non-participation. Randomised trials and crossover clinical studies suggest that playing sport is associated with specific health benefits. Some sports have relatively high injury risk although neuromuscular training programmes can prevent various lower extremity injuries. Clinicians can influence a large number of patients through brief interventions that promote physical activity, and encouragement toward participation in sport for some physically inactive patients qualifies as evidence-based therapy. Exercise might also be considered as a fifth vital sign and should be recorded in patients' electronic medical records and routine histories.