Understanding the control strategies of quiet stance via a fractal dimension analysis of centre of pressure

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Doyle, Tim L. A.
Humphries, Brendan
Issue Date
Thesis (M.S.)
School of Physical Education
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Certain natural phenomena have been identified as having fractal properties in their patterns. That is, their seemingly random patterns contain a level of order and deterministic properties that are more complex than previously thought. Centre of Pressure (COP) traces are one of these phenomena. By using a fractal dimension analysis of COP, it is possible that we can gain more information about control during quiet stance than traditional analyses have previously allowed. This Thesis considered a group of young healthy participants and a group of elderly healthy participants to compare traditional measures of COP (range and velocity of sway, and total excursion area) against a fractal dimension analysis of COP. Results indicated that both types of analyses are able to distinguish between eyes open and eyes closed in the elderly group. However, the fractal dimension analysis more accurately detects differences between the participant groups when standing with their eyes closed. Based on these results it is suggested that a fractal dimension analysis is more informative about posture control than traditional measures. Recommendations for future research include the development of model that incorporates non-linear properties of control and for further work investigating gait and balance from a dynamical systems perspective.