The utilisation of perceptual information (for affordance) and risk of falls in older adults

Proposed supervisory team:

Director of Studies: Professor Keith Davids
Supervisor 1: Dr. Mohsen Shafizadeh

One important change in the control of movement due to ageing is deterioration of sensory perception and ability of muscles to contract forcefully and quickly, resulting in declines in functional movement capacities, such as walking independently. According to the theory of Ecological Dynamics, control of voluntary movements is founded on interactions between perception and action systems so that information from the environment is used to regulate action, and, in turn, voluntary movements facilitate perception. Older adults use different strategies for visual search (e.g., needing longer fixations of gaze on a target) and movement control (e.g., delayed onset of movement organisation). They employ compensatory mechanisms during walking to adapt to environmental constraints (e.g., different obstacles, surfaces, objects), because the degree of coupling between perception and action deteriorates with age. This study will examine perception-action coupling during walking and when negotiating surrounding dynamic and variable environments, in comparing two elderly groups with and without prior experiences of falling. They will be required to walk in an area occupied by obstacles of different heights, walls, stairs and moving objects (e.g. flashing lights). Their actions with respect to these external objects will be assessed through analysis of candidate perceptual variables such as relative distance to object, relative velocity and also inter-limb coordination (e.g. head-torso-hips) with a motion capture system.

This project has both short-term and long-term benefits for older adults in terms of health and wellbeing. The short-term benefits include understanding interactions between perceptual and motor systems in controlling gait in elderly individuals, how dynamic environments can be designed to provide rich and relevant information (affordances) to guide actions in elderly, and whether the risk of falling is closely associated with adaptive functions established through interactions of the body and environment. It is also important to understand whether non-fallers attune to different perceptual variables than fallers. Long-terms benefits could include development of understanding how to design activities to enhance perceptual-motor coupling during exercise sessions in a gym and at home to increase the capacity of older adults to walk independently and safely. Other design features could involve changing the physical environment to support visuo-motor capacities of elderly people (such as varying colour, texture, size and shape of objects and surfaces for walking).
Aims:
1- Determine the roles of perceptual information for regulating action (e.g. posture, dynamic balance and walking) in previous research.
2- Compare the candidate perceptual variables that fallers and non-fallers use to regulate actions during walking.

The first aim will be met by conducting a systematic review of relevant literature. The second aim will be met through a pilot study and an experiment in the field. The method of data collection will be field assessment through using a motion capture system. A survey study by a questionnaire will be used for collecting information on personal demographics. Participant recruitment and data collection will be carried out in the Academy of Sport and Physical Activity at Sheffield Hallam University.