Health benefits can be derived simply from becoming more physically active, but the greatest benefits come from engaging in planned and structured exercise. Cardiovascular risk factors can be reduced and physical fitness enhanced with low to moderate levels of physical activity (40-60% of a person's maximal aerobic capacity). Low- to moderate-intensity activity is less likely than vigorous exercise to cause musculoskeletal injury and sudden heart attack death during exercise (a very rare occurrence even for vigorous exercisers), while it is more likely to promote continued adherence to activity.
Current recommendations state that children and adults should strive for at least 30 minutes daily of moderate intensity physical activity. An alternate approach that may be equally beneficial would be to engage in 5 to 10 minute bouts of moderate intensity activity throughout the day, for a total accumulation of at least 30 minutes for adolescents and adults and 60 minutes for children. Walking briskly or biking for pleasure or transportation, swimming, engaging in sports and games, participating in physical education, and doing tasks in the home and garden may all contribute to accumulated physical activity.
Children and adults who already engage in regular activity may benefit from more vigorous activity. The specific amount of energy expenditure needed by children to decrease their risk of cardiovascular disease is not known; for adults, approximately 3 kcals/kg of body weight/day has been recommended. Weight in pounds can be converted to kg by dividing by 2.2. Thus, a 140-pound person (140/2.2 = 63.6 kg) should expend about 192 kcals/day (63.6 X 3).