Weight-bearing physical activity has beneficial effects on bone health across the age spectrum. Physical activities that generate relatively high-intensity loading forces, such as plyometrics, gymnastics, and high intensity training, enhance bone mineral accrual in children and adolescents. To assess the effects of physical activity on bone mass in humans the BMD (bone mineral density) is measured which is the amount of mineral measured per unit are or volume of bone tissue. Physical activity plays an important role in maximizing bone mass during childhood and the early adult years maintaining bone mass through the 5th decade, attenuating bone loss with aging, and reducing falls and fractures in the elderly.
Physical activity plays a very important role in maximizing bone mass in children and adolescents. There is some evidence that exercise induced gains in bone mass in children are maintained into adulthood so the peak bone mass developed during this time is essential in decreasing the risk of osteoporosis in further years to come. Therefore physical activity habits during childhood may have long-lasting benefits on bone health. Observations conclude that bone mass is higher in children who are physically active than in those who are less active. Furthermore bone mass is higher in children who participate in activities that generate high impact forces, for example gymnastics, than those who engage in activities that are lower impact forces (e.g. walking) or non weight bearing (e.g. swimming).
During adulthood, the primary goal of physical activity should be to maintain bone mass. Peak bone mass is thought to be attainted by the end of the 3rd decade, therefore the early adult years may be the final opportunity for its increase. At this stage it is unclear whether adults can increase bone mineral density through exercise training. When increases have been reported, it has been in response to relatively high intensity weight-bearing endurance or resistance exercise.
After the age of 40, bone mass decreases by about 0.5% per year or more, regardless of sex or ethnicity. In middle-aged and older adults benefits of exercise may be reflected by a reduction in the rate of bone loss, rather than an increase in bone mass. The rate of loss varies by skeletal region and is likely influenced by such factors as genetics, nutrition, hormonal status, and habitual physical activity, making it difficult to determine the extent to which the decline in bone mass is an inevitable consequence of the ageing process. A variety of types of exercise can be effective in preserving bone mass of older women as well as men.
In conclusion maintaining a vigorous level of physical activity across the life span is an essential component for achieving and maintaining optimal bone health. Physical activity habits during childhood may have long-lasting benefits on bone health. It is important to keep active because there profound effects of immobilisation and bed rest on bone loss, so even the frailest elderly should remain as physically active as their health permits to preserve skeletal integrity.