Ph.D. Student Aubree Marshall Publishes in the American Journal of Biological Anthropology

Department of Anthropology Ph.D. student Aubree Marshall and co-authors Jessica S. Wollmann (Radford University, University of Toronto), McKenzie Schrank (Radford University, University of Colorado), and Laura Tobias Gruss (Radford University) published in the American Journal of Biological Anthropology. The title of the article is “Tibial torsion and pressures in the feet during walking: Implications for patterns of metatarsal robusticity.” This article presents the result of six years of research conducted through the Biomechanics Lab at Radford University. This research explored the relationship between tibial torsion and foot angle during standing and walking, and how the findings compared to the metatarsal robusticity found at the site of Dmanisi. 

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Objectives: The Dmanisi Homo fossils include a tibia with a low degree of torsion and metatarsals with a pattern of robusticity differing from modern humans. It has been proposed that low tibial torsion would cause a low foot progression angle (FPA) in walking, and consequently increased force applied to the medial rays. This could explain the more robust MT III and IV from Dmanisi. Here we experimentally tested these hypothesized biomechanical relationships in living human subjects. 

Materials and Methods: We measured transmalleolar axis (TMA, a proxy for tibial torsion), FPA, and plantar pressure distributions during walking in young men (n=40). TMA was measured externally using a newly developed method. A pressure mat recorded FPA and pressure under the metatarsal heads (MT I vs. MT II–IV vs. MT V). 

Results: TMA is positively correlated with FPA, but only in the right foot. Plantar pressure under MT II–IV does increase with lower TMA, as predicted, but FPA does not affect pressure. Body mass index also influenced plantar pressure distribution.

Discussion: Lower tibial torsion in humans is associated with slightly increased pressures along the middle rays of the foot during walking, but not because of changes in FPA. Therefore, it is possible that the low degree of torsion in the Dmanisi Homo tibia is related to the unusual pattern of robusticity in the associated metatarsals, but the mechanism behind this relationship is unclear. Future work will explore TMA, FPA, and plantar pressures during running.