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

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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.