Role of impact activity in peripubertal bone accrual

达到最大峰值骨量是预防骨质疏松症的关键。因为大部分骨量是在青春期周围积累的，所以增加骨量峰值的干预措施应该针对这一时期。体育活动是促进骨骼积累的重要可调节因素，但尚不清楚儿童时期积累的益处是否能维持到骨骼成熟。这一建议检验了下列假设：(I)参加冲击活动的女孩在青春期周围比不参加的女孩积累更多的骨骼，即使在活动停止后也将保持这些益处；（II）骨几何形状的增加比骨材料性能的增加对骨量增加的贡献更大。为了验证这些假设，提出了以下具体目标：(1)纵向测量青春期前和青春期前后的体操运动员，退役体操运动员和非体操运动员对照的骨累积和冲击活动量，将进行为期3年的随访，从平均11年开始。记录每周的体操活动时间，并通过问卷调查测量运动量。在基线和6个月的间隔将进行人体测量，记录自我坦纳阶段，并进行半定量食物频率问卷调查。每隔一年进行一次生物电阻抗分析、肌肉力量和耐力测量，并进行双能x射线吸收仪（DXA）扫描。（II）纵向测量相同活动和对照队列的骨几何形状和骨矿物材料特性。DXA扫描将用于评估骨几何形状以及骨和对照队列的差异。DXA扫描将用于评估骨几何形状和骨体积密度活动与不活动儿童的差异。对所提出的假设的确认将肯定儿童运动对骨骼生长的重要性，为这种活动的保护作用提供证据。

Attainment of maximal peak bone mass is crucial in the prevention of osteoporosis. Because a majority of bone mass is accrued during the peri- pubertal years, intervention designed to increase the peak should target this period. Physical activity is an important modifiable factor contributing to bone accrual, yet it is unclear whether benefits accrued during childhood are maintained to skeletal maturity. This proposal tests the following hypotheses: (I) Girls who participate in impact activity will accrue greater amounts of bone during the peripubertal years than inactive girls, and will retain those benefits even after cessation of the activity; (II) Increases in bone geometry will provide a greater contribution to bone mass gain than increases in bone material properties. To test these hypotheses the following Specific Aims are proposed: (I) To longitudinally measure bone accrual and the amount of impact activity in a cohort of pre- and peri-pubertal gymnasts, retired gymnasts, and non- gymnast controls will be followed for a 3 year period, beginning at an average of 11 years. Hours per week of gymnastics activity will be recorded and amount of physical activity will be measured by questionnaire. At baseline and six month intervals anthropemetric measurements will be made, self-Tanner stage will be recorded, and a semi-quantitative food frequency questionnaire will be administered. At yearly intervals bioelectric impedance analysis, muscle strength and endurance will be measured, and dual energy x-ray absorptiometry (DXA) scans will be performed. (II) To longitudinally measure bone geometry and bone mineral material properties in the same activity and control cohorts. DXA scans will be used to assess differences in bone geometry and in bone and control cohorts. DXA scans will be used to assess differences in bone geometry and in bone volumetric density activity vs. inactive children. Confirmation of the proposed hypotheses will affirm the importance of childhood activity in bone accrual, providing evidence of the protective effect of such activity.