Physical activity in childhood has potential benefits for bone health and many other health outcomes. A number of studies have demonstrated that exercise can enhance bone gains in children and adolescents. Activities that impose high loads on bone seem most effective, and relatively brief bouts of such exercise are adequate. Exercise seems to be most effective during early puberty, and some benefit of childhood exercise seems to be retained longer term, whilst in adults exercise effects on bone seem to be reversed on cessation. Activity that produces sustained increases in heart rate and energy expenditure can help with weight control and cardiovascular fitness, which may reduce risk of future cardiovascular disease and type 2 diabetes. Unfortunately, many children and adolescents (particularly adolescent girls) do not meet the recommended 60 minutes per day of exercise and it is unclear how many do adequate "bone-loading" exercise to optimise bone accrual. Increasing the amount of exercise, and incorporating "bone loading exercise" may thus be beneficial in children and adolescents.