Nonlinear analysis of the development of sitting postural control

The development of sitting postural control in five normal infants was examined longitudinally at three stages of sitting: Stage 1, when infants could hold up their head and upper trunk, but could not sit independently; Stage 2, when infants began to sit independently briefly; and Stage 3, when infa...

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Bibliographic Details
Published in:Developmental psychobiology 2003-05, Vol.42 (4), p.368-377
Main Authors: Harbourne, Regina T., Stergiou, Nicholas
Format: Article
Language:English
Subjects:
Child Development
complexity
dimensionality
Entropy
Female
Humans
infancy
Infant
Male
Nonlinear Dynamics
Posture
sitting postural development
stability
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Summary:The development of sitting postural control in five normal infants was examined longitudinally at three stages of sitting: Stage 1, when infants could hold up their head and upper trunk, but could not sit independently; Stage 2, when infants began to sit independently briefly; and Stage 3, when infants could sit independently. Methods from nonlinear dynamics were used to analyze center of pressure (COP) data during sitting in terms of stability of the neuromuscular system (Lyapunov Exponent), movement dimensionality (Correlation Dimension), and complexity/regularity (Approximate Entropy). Results indicated significant changes in the nonlinear measures over time, with increased stability and increased regularity revealing a more stable and periodic strategy of maintaining postural control. Dimensionality decreased from Stage 1 to 2, indicating a constraint of the degrees of freedom. Subsequently, dimensionality increased from Stage 2 to 3, indicating a release of the degrees of freedom as sitting independence emerged. Nonlinear analysis of the COP time series supports the perspective that the development of postural control is a dynamic process whereby the infant learns to control the body's degrees of freedom to achieve the sitting posture. © 2003 Wiley Periodicals, Inc. Dev Psychobiol 42: 368–377, 2003.
ISSN:0012-1630
1098-2302
DOI:10.1002/dev.10110