School of Geosciences (ETDs)

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Browsing School of Geosciences (ETDs) by Author "Carlson, Kristian J."

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    An investigation into high gear and low gear propulsion in human gait and its relation to metatarsal diaphyseal geometric cross-sectional properties
    (University of the Witwatersrand, Johannesburg, 2023-06) Reyneker, Mark Brenden; Carlson, Kristian J.; Zipfel, Bernhard
    This study investigates the relationship between metatarsal bone form, as quantified by cross-sectional geometric properties, and its relationship to high (medial forefoot loading) versus low gear (lateral forefoot loading) push-off during the propulsion phase of the gait cycle. The objective being to assess whether forefoot loading may be variable or whether high gear loading occurs in higher frequencies, as depicted in theoretical foot function models. The study sample (n=53), made up of three broad groups, include Later Stone Age southern Africans, post-industrial individuals from South Africa, and the Jomon of Japan. Metatarsals 1-5 cross-sectional geometric properties (CSA, Ix, Iy, Imin, Imax, Zx, Zy, Zp, Zmin, Zmax) taken from CT scans at 25%, 35%, 50% and 65% metatarsal diaphyseal biomechanical lengths are grouped into high gear (metatarsal 1-2) and low gear (metatarsal 2-5) for comparison. The combined population analysis reveals that the high gear metatarsal diaphysis exhibit significantly higher strength and rigidity driven mainly by the post-industrial individuals from South Africa and the Later Stone Age southern Africans. In contrast, the Jomon of Japan, exhibit no significant differences between high and low gear metatarsals except for CSA, Imax, and Zmax. Furthermore, metatarsal 1 and 5 differ far less in cross-sectional geometric properties in the Jomon of Japan compared to the other populations except for medial-lateral strength (Zy) and torsional and average bending strength (Zp) where metatarsal 5 is significantly higher. The study findings indicate that forefoot loading demonstrates variability during the propulsion phase of gait, while also suggesting a higher frequency of occurrence for high gear push-off. This challenges current theoretical models of foot function that emphasise high gear push-off as typical and normal for striding bipedalism.