Date of Award

6-1999

Degree Type

Thesis

Degree Name

Master of Science (MSc)

Department

Human Biodynamics

Supervisor

C.l. Riach

Language

English

Abstract

The purpose of this longitudinal study was to determine whether a non-monotonic pattern characterizes the development of postural control in children from age 5 to 8 years, as suggested by previous cross-sectional studies. Postural control was considered in terms of control strategy and its variability operationalized by mean and standard deviation of Centre of Pressure velocity (COPvel); and of effectiveness and its variability operationalized by mean and standard deviation of COP anteroposterior excursion (YS). Periods of significant variability were used to indicate behavioural transitions. Seventeen, healthy children (9 males, 8 females) aged 5 to 6 years (61.5 - 75 months) were tested at 3 to 4 month intervals until age 8 years (83 - 97 months) in eyes-open quiet stance (OS) on a force platform for 30 seconds in each of 10 trials. Data were reorganized into 6 developmental categories based on adjacent test dates prior to (-2, -1) and after (+1, +2, +3) a subject's trial with the lowest COPvel. Developmental category is proposed to represent level of sensorimotor integrative skill. A 1-way MANCOVA revealed a significant effect ( p <.0001) for developmental category with covariance due to height, weight and actual age removed. Post-hoc 1-way ANCOVAs showed a significant effect (p<.OOO1) on measures of strategy. However differences in COPvel (type of strategy used) and differences in its variability (denoting a transition between types of strategies) were not always coincident. Performance outcome (yS) changed linearly across categories. From a consideration of the results it was concluded that a non-monotonic change in control strategy describes the development of quiet stance equilibrium. A transition, marked by variability of COPvel occurs from a primarily open-loop to incorporation of open- and close-loop components of control. Honing of strategy used precedes and follows transitions. Constriction of velocity and excursion may typify the early stages of bi-modal strategy use suggesting instability in realworld situations at this stage. Linear change in effective excursion regardless of strategy employed in unchallenged as may decrease the utility of this measure in assessing stability status in children. Developmental categories describe affiliation with the strategy employed and may represent differentiable levels of sensorimotor integrative skill. As such, they may be more useful in assessing progression of equilibrium control than consecutive age in years.

McMaster University Library

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