Whole-body coordination such as in sit-to-stand (STS) movements is an important activity of independent daily living that is affected by decreased muscular strength and postural control due to ageing and also as a result of neurological diseases such as stroke. Recent research has taken an interest in using motor imagery for rehabilitation and training because it has many features in common with movement execution without some of the practical difficulties of repeated physical practice. Imagery tends to be more effective when it takes a first person perspective and focuses on kinesthetic aspects of movement. On the contrary, research in exercise science shows that movement execution is more fluent when attention is focused on body-external perceptual consequences of movement. How ageing affects this difference in the impact of attentional focus is not well understood. This thesis examines the effects of body-external (visual) and body-internal (muscular or somatosensory) attentional focus on STS movement execution and imagery in healthy young and older adults. The thesis reports four experiments comparing execution and imagery performance in young and older adults. Experiment 1 was designed to clarify the impact of attentional focus on motor performance and imagery in young and older adults. Experiment 2 examined the impact of changing the level of effort (by manipulating the starting seat height) on the effects of attentional focus. Experiment 3 measured the impact of unimanually balancing a load in the hand on the role of attentional focus in physical and imagined STS movements. Experiment 4 studied the role of attentional focus in a training protocol employing motor imagery practice. Postural transition duration and transition stability during physical trials, self-reported movement times during physical and imagined trials, and ground reaction force and vividness of imagery during imagined trials were recorded. The results show that focusing attention on muscular effort not only benefitted older people’s motor performance, but also increased both the level and task-linked modulation of inadvertent force production during imagery (Experiment 1). Increasing the level of effort (by lowering seat height) resulted in better modulation of movement time as a function of effort level when older adults focused attention internally (Experiment 2). When a secondary task of holding a fluid container upright was added, external attentional focus benefitted both age groups (Experiment 3), indicating that the effects of attentional focus are task-linked. There was also a numerical indication that focusing attention on muscular load during motor imagery-based practice may be more effective in older adults (Experiment 4). These results suggest that kinesthetic imagery may be particularly consonant with the more internally focused motor control that benefits older people. Thus, training or rehabilitation protocols using kinesthetic imagery may serve more effectively as a form of practice for this age group by activating neural pathways similarly to their motor execution. On the other hand, young people consistently performed better under external attentional focus, and even modulated their force production during imagery better when externally focused. The focus on musculoskeletal dynamics that kinesthetic imagery requires may therefore correspond less closely to motor planning and control processes in this age group. Thus, pathways by which kinesthetic imagery can serve as practice are likely to be more indirect than for older people. These findings provide fundamental knowledge for further clinical research on patients who suffer disability in STS movements.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:618959 |
| Date | January 2014 |
| Creators | Srisupornkornkool, Kanokwan |
| Publisher | University of Warwick |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://wrap.warwick.ac.uk/62781/ |
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