The effects of gaze control and body segment recoupling on human gait and foot pressure variability : a modern and evolutionary perspective

• Main Author: Webster, Emma
• Published: University of Liverpool 2014
• Subjects: 612.7
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.682423

This thesis investigates the relationships between gaze control, body segment coupling, and foot pressure patterns during walking, and discusses the resulting implications for both modern humans and our evolution. One of the major changes thought to underlie the transition between Australopithecus and Homo is the decoupling of the head and shoulders, and trunk and hips. The independent rotation of these segments enables greater control of the torque and free moments resulting from leg swing, and is considered key in the control of bipedal locomotion. Fossil evidence of semicircular canal morphology (Spoor et al., 1994) also indicates congruent changes in the vestibular system, which alongside the ability to track moving objects with clarity using smooth pursuit eye movements, are likely to have been fundamental to sensory integration and prioritisation during locomotion. This research therefore assesses how the increased neurological demands of active visual tracking in environments of varying visual complexity, and the artificial recoupling of body segments, impact on foot pressure variability during locomotion in modern man. The results demonstrate that foot pressure variability appears unaffected by larger levels of background visual clutter when tracking using smooth pursuit eye movements - variability appears to be higher in very low levels of visual clutter when there is a relative absence of visual referents. This variability was found to further increase when undertaking a secondary auditory task whilst compared to visual tracking alone. When considering the effects of experimental recoupling of body segments, an increase in foot pressure variability was also observed when compared to natural unrestricted walking, with increased arm and leg swing appearing to compensate for reduced hip and shoulder rotations. These changes in foot pressure variability indicate less consistent gait patterns, and suggest the utilisation of postural correction mechanisms, such as the lateral ankle strategy, to remain stable. The normal ageing process, and resulting joint stiffness and visual, vestibular, and cognitive decline, may be expected to exacerbate such variability increasing the likelihood of falls. This research therefore not only contributes to the understanding of potential locomotor strategies in early hominins, but also has significant implications for the safety of the elderly and infirm during locomotion, particularly with respect to the built environment.