Doctoral Dissertation Improvement: Morphological and Functional Correlates of Variation in the Human Longitudinal Arch

纵向足弓被认为是人类足部的一种独特适应，对足部的正常功能至关重要。在双足行走时，足弓支撑身体的重量，并将脚转变为推进杠杆。然而，人类足弓高度变化，沿着从平坦到非常拱形的连续体（通常是渐进的），这质疑了发育良好的足弓对于健康的足部功能至关重要的概念。我们对这种变化的理解是不完整的;更具体地说，研究缺乏对脚骨变化对足弓高度变化的影响程度的认识，以及现代人类的足弓结构如何反映人类进化史的进程。博士生Amber Heard-Booth（在德克萨斯大学奥斯汀分校Liza Shapiro博士的监督下）的这篇论文项目旨在提高我们对纵弓进化历史的认识，以便我们可以更彻底地了解其在现代人类中的变化基础。该研究将1）确定直接有助于纵向足弓高度的脚骨特征; 2）将这些骨骼特征与足部支撑体重的方式（足底压力）联系起来; 3）使用这些信息来估计足弓高度并从古人类的足部化石中重建足部负荷（即，两足动物的祖先）。脚骨，足弓高度和足底压力之间的关系将通过研究考古样本中的脚骨发育和活着的孩子的足弓发育来评估;因此，它代表了第一个采取个体发育的观点，并充分利用已知足弓高度不同的人类脚样本。还将使用磁共振成像（MRI）和足底压力数据在成人样本中研究这些变量之间的关系。通过提供有关发育中和成年人足部的足部骨骼形状和功能之间关系的知识，该项目将告知临床医生对足弓发育变化范围的理解，这可能有助于评估矫形器的需求，同时了解足弓高度的变化如何与足底压力相关，这将有助于临床医生选择干预措施以防止压力相关损伤。该研究还通过为德克萨斯大学的学生提供研究机会，特别是通过参与针对第一代本科生的实习计划，促进科学教育。

The longitudinal arch is considered to be a unique adaptation of the human foot that is crucial for proper foot function. During bipedal walking, the arch supports the weight of the body and transforms the foot into a propulsive lever. Human arch height varies, however, along a continuum from flat to very arched (often asymptomatically), which questions the notion that a well-developed arch is essential for healthy foot function. Our understanding of this variation is incomplete; more specifically, research is lacking in appreciation for the degree to which variation in foot bones contributes to variation in arch height, as well as how the arch structure seen in modern humans reflects the course of human evolutionary history. This dissertation project by doctoral student Amber Heard-Booth (under the supervision of Dr. Liza Shapiro, University of Texas at Austin) aims to improve our knowledge of the evolutionary history of the longitudinal arch so that we may more thoroughly understand the basis for its variation among modern humans. The research will 1) identify foot bone features that directly contribute to longitudinal arch height; 2) link these bony features to the way in which the foot supports body weight (plantar pressure); and 3) use this information to estimate arch height and reconstruct foot loading from the foot fossils of hominins (i.e., bipedal human ancestors). The relationship between foot bones, arch height, and plantar pressure will be assessed by studying both foot bone development in archaeological samples and the development of the arch in living children; as such, it represents the first to take an ontogenetic perspective and to fully utilize a sample of human feet known to vary in arch height. The relationship among these variables also will be investigated in an adult sample of humans using magnetic resonance imaging (MRI) and plantar pressure data. By contributing knowledge on the relationship between foot bone form and function in developing and adult human feet, this project will inform clinicians' understanding of the range of variation in arch development, which may help assess need for orthotics, while understanding how variation in arch height is linked to plantar pressure will help clinicians choose interventions to prevent pressure-related injuries. The research also fosters scientific education through provision of research opportunities to students at The University of Texas, especially through engagement with an internship program that targets first-generation undergraduates.