comparison of the extent of exercise effects on bone mineral density of boys of ilam city

background: the extent of bone minerals density (bmd) gained during childhood is good index for bmd in adulthood. recent studies imply that exercise increases bmd however, there are rare studies about the best ages in which exercise gives the highest effect on children’s bmd. this study was carried out with the aim of comparing the extent of exercise effect on various ages on bmd of boys of ilam city. methods: a total of 60 boys of ilam city was selected randomly and were divided in two groups (the experimental and the control). next, each group was subdivided into three age groups 6-8 yrs, 8-10 yrs and 10-12 yrs. then their height, weight, body mass index (bmi) and bmd in femur neck and lumbar vertebrae (l2-l4)) were measured using dual energy x-ray absorptiometry machine (dxa machine). subsequently, the experimental group performed special exercises for 12 weeks, three sessions per week and 60 minutes per session. after three months, the bmd of both groups was remeasured. results: our findings indicated that exercise increases the bmd of children (in femur neck and lumbar spine area) in any age and such increase is more obvious in 8-10 years old boys than the other groups. the difference in bmd of lumbar spine before and after exercise in children 8-10 years is significant (bmd of before exercise = 601 mg/cm2, bmd of after exercise = 613 mg/cm2), (t= - 3.502, p= 0.007).conclusion: exercise and physical activity during childhood, particularly in 8-10 years old kids result in bmd increase. therefore, it is proposed that exercise and physical activity in children (particularly in 8-10 years old) is very effective to decrease osteoporosis outbreak during adulthood.