Variations in Cortical Bone Responses to Exercise-Induced Loading

本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），骨骼替换旧的、受损的组织。初步数据表明，生长与修复的相对百分比在个体中呈负向变化，四肢附近的生长更多，远端则发生更多的重塑。有人提出，生长优先发生在额外质量增加成本低的地方，但修复在诸如肢体末端等区域受到青睐，那里的质量增加会带来指数级高的能量消耗，因此往往更薄更弱。对负载的生长和修复反应的调节表明，骨骼的不同区域适应不同的应变水平。这一建议对人类和其他脊椎动物的人类学、古生物学和其他骨学研究具有重要意义。人们特别感兴趣的是验证这样一个假设，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，因为他们的机械负荷普遍较低，尤其是在童年时期。

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.