Variations in Cortical Bone Responses to Exercise-Induced Loading

该项目研究运动对骨骼的影响，重点关注骨骼对负荷做出反应的两个最重要的过程：(1)生长(建模)，骨骼增加其大小；(2)修复(哈弗斯重塑)，骨骼取代陈旧的受损组织。初步数据显示，在四肢以下的个体中，生长与修复的相对百分比往往是相反的，更多的生长发生在身体中心附近，更多的重塑发生在身体的远端。有人提出，增长优先发生在额外质量增加的成本较低的地方，但修复倾向于在肢体末端等质量增加带来指数级更高的能量成本的区域，因此这些区域往往更薄和更弱。对负荷的生长和修复反应的调节表明，骨骼的不同区域适应于耐受不同的菌株水平。这一建议对人类学、古生物学和其他关于人类和其他脊椎动物的骨学研究具有重要意义。尤其令人感兴趣的是验证一种假设，即近代工业时代的人类总体上比狩猎采集者和早期农民的骨骼更薄，因为机械负荷通常较低，特别是在儿童时期。

This project studies the effects of exercise on bones, focusing on the two most important processes by which bones respond to loading: (1) growth (modeling) in which a bone increases its size, and (2) repair (Haversian remodeling) in which bones replace old, damaged tissue. Preliminary data indicate that the relative percentage of growth versus repair tends to vary within individuals inversely down the limbs, with more growth occurring near the body's center and more remodeling occurring distally. It is proposed that growth preferentially occurs where there is a low cost to additional mass increase, but that repair is favored in regions such as the ends of the limb where mass increases impose an exponentially higher energetic cost and which, therefore, tend to be thinner and weaker. Modulation of growth versus repair responses to loading suggest that different regions of the skeleton are adapted to tolerate different strains levels. This proposal has significance for anthropological, palaeontological and other osteologcial research on humans and other vertebrates. Of special interest is testing the hypothesis that recent, industrial-era humans tend to have overall thinner bones than hunter-gatherers and early farmers because of generally low levels of mechanical loading, particularly during childhood.