Benefits, Harms, and Costs Cohort studies report a consistent, strong, graded association between physical activity and incidence of CHD in men. Insufficient evidence exists for women. Prospective population studies and experimental studies on the secondary prevention of obesity found that increased relative risk for significant weight gain was associated with low physical activity level. Exercise alone had a significant effect on weight, but a combination of diet and exercise was most effective for preventing obesity and maintaining ideal body weight. Potential adverse effects of exercise include injury, osteoarthritis, myocardial infarction and sudden death.
Few data exist on the incidence of injury during non-competitive sports.
Injuries are often due to excessive levels of activity or improper techniques, and, therefore, are preventable. Both studies reported a protective effect of regular physical activity. Another study found an increased risk for sudden death among sedentary individuals who engaged in vigorous activity. Studies on the effectiveness of physician counselling provide little information on long-term compliance and have limited generalizability. Citations in support of individual recommendations are identified in the guideline text.