Effects of Jumping on Growing Bones

In this study we will investigate the effects of a high-impact exercise program involving jumping on bone mass (the amount of bone) of the hip and backbone in the growing skeleton. We will also look at the effects of gradually stopping the jumping program on bone mass in the growing skeleton. A high-impact exercise program may build more bone during childhood, while the skeleton is still growing. This may help prevent broken bones due to loss of bone mass later in life. We will recruit 200 children aged 5-10 to participate in the study. For 6 months we will train the children in either a jumping or stretching program. We will then gradually reduce the amount of exercise over 6 months. We will measure bone mass in the hip and backbone at the start of the study, after jumping, and 6 months after the jumping program is stopped. We will compare the results in the jumping and stretching groups.