The effect of loading on the size, shape and strength of cortical bone during different stages of maturation

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Osteoporosis is a condition in which the skeleton becomes fragile and susceptible to fractures. It is a public health problem that affects both men and women over the age of sixty. Although osteoporosis affects the elderly, the most opportune time to prevent osteoporosis may be during childhood. Physical activity is a lifestyle factor known to affect the strength of the skeleton. Bone density is commonly used as a measure of bone strength because it is easily measured and is related to the breaking strength of bones. However changes in the shape of bones can also affect bone strength with or without an increase in bone density. Changes in bone shape in response to exercise in children or adults have rarely been investigated, and little is known about the effects of exercise on bone shape during different stages of growth. This study is the first to investigate how exercise during childhood may affect bone strength by changing bone shape. 45 elite female tennis players aged between 6 to 18 years have completed two years of this study. 90 novice and competitive male tennis players aged between 6 to 20 years and 60 healthy age matched controls will be asked to participate in this study. Measurements will be made annually for three years. The bone shape and density of the dominant and non-dominant arms of the players will be compared with the children who don't play tennis - comparisons will also be made between i) different stages of puberty and ii) girls and boys. The findings of this study are important because the lifestyle of children today may predispose them to a greater risk of osteoporosis late in life. Physical activity may be the most important modifiable protective factor against fragile bones in old age. The findings of this study will be the first to provide insight into whether there is a unique time during growth when exercise will result in the greatest increase in bone strength by changing bone shape.