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Longitudinal Development of the Automatic Postural Response in Infants.
H. Sveistrup1, M. H. Woollacott
1Department of Occupational Therapy, Faculty of Health Sciences, University of Ottawa, 451 Smyth, Ottawa, Ontario 1H 8M5, Canada.
Journal of Motor Behavior
|March 1, 1996
Summary
Infants develop automatic postural responses by coordinating muscle activation, progressing from single muscles to functional synergies. This sensory-motor development continues even after independent walking begins.
Area of Science:
- Developmental motor control
- Neuroscience
- Biomechanics
Background:
- Postural control is crucial for independent movement.
- The development of automatic postural responses (APRs) in infants is not fully understood.
- Understanding APR development informs interventions for motor impairments.
Purpose of the Study:
- To investigate the developmental trajectory of automatic postural responses in infants.
- To analyze muscle activation patterns and timing during postural perturbations.
- To determine how sensory-motor organization evolves during early locomotion.
Main Methods:
- Longitudinal study of 9 infants from pre-independent standing to independent walking.
- Surface electromyography (sEMG) recorded leg and trunk muscle activity.
- Analysis of muscle onset latencies and activation consistency following support surface translations.
Main Results:
- Infants initially activated muscles in isolation or pairs, progressing to functional synergies.
- Three-muscle postural responses were inconsistent in younger, non-walking infants.
- The proportion of trials with muscle activity increased significantly (p < .05) post-independent walking.
Conclusions:
- Automatic postural responses develop progressively, starting with simpler muscle activations.
- Functional muscle synergies emerge as infants gain postural control and independent walking skills.
- This study highlights the maturation of sensory-motor organization during infant development.