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

纵向足弓被认为是对人类足部的一种独特的适应，这对足部的正常功能至关重要。在两足行走过程中，足弓支撑身体的重量，并将脚转变为推进杠杆。然而，人体的足弓高度在从平坦到拱形(通常是无症状)的连续体中变化，这质疑了发育良好的足弓对于健康的脚功能至关重要的观点。我们对这种变异的理解是不完整的；更具体地说，对于足部骨骼的变异在多大程度上影响了拱门高度的变化，以及现代人看到的拱形结构如何反映人类进化史的进程，研究缺乏认识。这篇由博士研究生Amber Hed-Booth(由德克萨斯大学奥斯汀分校Liza Shapiro博士指导)的论文旨在提高我们对纵弓的进化史的认识，以便我们可以更彻底地了解它在现代人中变异的基础。这项研究将1)确定直接影响足弓纵向高度的足部骨骼特征；2)将这些骨骼特征与脚支撑体重的方式(足底压力)联系起来；3)利用这些信息估计足弓高度，并根据古人(即两足人类祖先)的足部化石重建足部负荷。将通过研究考古样本中的足骨发育和在世儿童的足弓发育来评估足骨、弓高度和足底压力之间的关系；因此，这是第一次从个体发生学的角度并充分利用已知足弓高度不同的人类脚样本。这些变量之间的关系也将在成人样本中使用磁共振成像(MRI)和足底压力数据进行研究。通过提供有关发育和成人足部骨骼形态和功能之间关系的知识，该项目将使临床医生了解足弓发育的变异范围，这可能有助于评估矫形术的需求，同时了解足弓高度变化与足底压力的关系将帮助临床医生选择预防压力相关伤害的干预措施。这项研究还通过向德克萨斯大学的学生提供研究机会来促进科学教育，特别是通过参与一个针对第一代本科生的实习项目。

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.