PhD Studentships |
Current Scholarships
Investigating the ultimate costs of legged locomotion and constraints to their reduction
Supervisors: Dr Jim Usherwood (jusherwood@rvc.ac.uk) and Dr Monica Daley
Department: Veterinary Basic Sciences
Animals get tired when they walk, trot, run or gallop. Energy cost is a critical factor in gait selection by animals. Surprisingly, we do not yet understand the causes of this cost. The goal of this project is to identify the ultimate origins of energy cost of locomotion. This project has a basic science focus, but also has clear implications for health and welfare of humans and animals. By identifying the ultimate sources of cost, we can guide assistance and rehabilitation strategies to manipulate cost and improve mobility in individuals vulnerable to fatigue (for example, ageing and obese individuals).
Energy losses dictate the amount of muscle work required to maintain movement. Some energy loss can be attributed to aerodynamic drag and surface friction. However, legged locomotion is very much more costly than rolling on wheels: consider the success of cycling. Existing ‘phenomenological’ models successfully predict the energy cost of legged locomotion; however, the underlying mechanisms – the ultimate ‘why’ – remain obscure. This project will develop new models of basic mechanisms and test their predictions using experimental manipulation of human and bird locomotion. Forceplate and metabolic gas measurements will show the kinetics and energetics of locomotion, and these will be compared with the theoretical predictions developed from reductionist mechanics and optimization approaches.
While energetic minimization, constrained by physiological realities, will be the central thrust of the project, alternative selective pressures (such as stability) will also be considered. For instance, why do small birds run with such compliant legs? Energetically, this may allow relatively small losses from inelastic loading of the guts; alternatively, compliant legs might increase robustness (relating to stability) in uneven terrain. Why do humans skip only rarely, and never at very high speeds? Can a fuller understanding of the locomotor costs predict gait selection and top sprinting speeds?
References:
- Usherwood, J.R., Williams, S.B. and Wilson, A.M. (2007). Mechanics of dog walking compared with a passive, stiff-limbed, 4-bar linkage model, and their collisional implications. J. Exp. Biol. 210, 533-540. doi: 10.1242/jeb.02647
- Usherwood, J.R., Szymanek, K. L. and Daley, M.A. (2008). Compass gait mechanics account for top walking speeds in ducks and humans. J. Exp. Biol. 211, 3744-3749.
- Daley, M.A. and Usherwood, J.R. Potential accounts for the ‘Groucho-running paradox: Benefits of compliant legs for economy, robustness and injury avoidance’. In Review.
The deadline for applications is Friday 12th February 2010.
Interview Dates:
Friday 12th March 2010 (Hawkshead Campus)
Tuesday 16th March 2010 (Camden Campus).
See the main Studentships page for application details and further information.