Role of impact activity in peripubertal bone accrual

达到最大峰值骨量是预防骨质疏松的关键。由于大部分骨量是在青春期前后积累起来的，所以旨在提高青春期骨量峰值的干预措施应该针对这一时期。体力活动是导致骨骼增加的一个重要的可修改因素，但尚不清楚儿童时期积累的好处是否保持到骨骼成熟。这一建议检验了以下假设：(I)参加撞击活动的女孩在青春期周围几年比不活动的女孩积累更多的骨骼，即使在活动停止后仍将保留这些好处；(Ii)骨骼几何形状的增加将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：(I)纵向测量青春期前和青春期前体操运动员、退役体操运动员和非体操运动员对照组的骨累积量和冲击性活动量，从平均11年开始，为期3年。每周的体操活动时间将被记录下来，体力活动量将通过问卷调查来衡量。在基线和6个月间隔进行人体测量，记录自我晒黑阶段，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，测量肌肉力量和耐力，并进行双能X射线吸收法(DXA)扫描。(Ii)纵向测量同一活动中的骨几何形状和骨矿物材料特性，并控制队列。DXA扫描将被用来评估骨骼几何以及骨骼和对照队列的差异。DXA扫描将被用来评估骨几何形状和骨体积密度活动与不活动儿童的差异。对提出的假说的确认将肯定儿童活动在骨积累中的重要性，为此类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.