Grant, Barbara 
ORCID: 0000-0003-2771-7733
(2023)
How are human gait and energetics modified when walking over substrates of varying compliance?
PhD thesis, University of Liverpool.
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Abstract
Locomotion in the real-world requires humans to negotiate a variety of surfaces that have different material and mechanical properties and thus, require gait adjustments to maintain stability and efficiency. However, our current understanding of human gait and energetics is dominated by studies on hard, level surfaces in a laboratory environment. Previous research has shown that when walking on more irregular terrains such as loose rock surfaces, uneven surfaces and compliant substrates such as snow, grass and sand, there is an increase in energy expenditure. However, the primary mechanistic causes of this increase in energy costs is unclear. Previous studies suggest various biomechanical mechanisms including disruption to pendular energy recovery, increased muscle work, decreased muscle-tendon efficiency and increased gait variability. Yet, comparisons between studies is hindered by the measurement of different variables across studies and variation in substrates used. In this thesis, I focus on human walking over compliant substrates. This thesis aims to improve our understanding of the relationship between energetic costs, substrate properties, gait biomechanics and muscle activities. This is done by presenting a large experimental data set of human walking on both artificial (foam) and natural (sand) compliant substrates. The studies showed that compliant substrates had a considerable effect on gait biomechanics, muscle activation and energetics. On foam, there was greater energetic expenditure on more compliant substrates. On all compliant substrates, participants displayed greater ankle dorsiflexion during stance and greater knee and hip flexion during swing, increased muscle activation and changes to spatiotemporal parameters such as increased cycle time, stance time and swing time and decreased walking speed. The findings of this thesis suggests that overall gross adaptations like sagittal kinematics, spatiotemporal parameters and muscle activation are adopted in response to the depth of depression into a compliant substrate. However, there are specific gait changes due to substrate properties. Further research is required to explore gait adaptations on substrates with different material and mechanical properties. Furthermore, some of our results suggest there is large participant variability even in a relatively homogeneous study population. Therefore, future work should not only look at other demographic groups but also explore individual participant differences such as gender effects and variations in anatomical parameters.
| Item Type: | Thesis (PhD) |
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| Divisions: | Faculty of Health and Life Sciences |
| Depositing User: | Symplectic Admin |
| Date Deposited: | 05 Apr 2023 10:43 |
| Last Modified: | 05 Apr 2023 10:43 |
| DOI: | 10.17638/03168955 |
| Supervisors: |
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| URI: | https://livrepository.liverpool.ac.uk/id/eprint/3168955 |
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