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Updated: Aug 21, 2026
Assessment and Evaluation of the High Risk Neonate: The NICU Network Neurobehavioral Scale
Published on: August 25, 2014
Muscle responses to seated perturbations for typically developing infants and those at risk for motor delays
Kathleen Washington1, Anne Shumway-Cook, Robert Price
1Division of Physical Therapy, Department of Rehabilitation Medicine, University of Washington, 1959 NE Pacific, Seattle, WA 98195-6490, USA. kwpt@u.washington.edu
Insights
High-risk infants showed less organized muscle responses to balance challenges compared to typically developing infants. This suggests complex, though sometimes immature, postural development in infants with neuromotor delays.
Area of Science:
- Developmental neuroscience
- Motor control
- Pediatric physical therapy
Background:
- Infants' ability to maintain balance is crucial for motor development.
- Understanding muscle activity patterns in response to perturbations is key to identifying neuromotor delays.
Purpose of the Study:
- To compare the muscle activity responses to seated forward perturbations between typically developing infants and those at risk for neuromotor delays.
- To investigate the spatial and temporal organization of muscle activity in these groups.
Main Methods:
- Surface electromyograms were used to record muscle activity in the neck, trunk, and leg.
- Center of pressure measures were collected during forward platform perturbations.
- Participants included 12 typically developing and 12 high-risk infants aged 8-10 months.
Main Results:
- Typically developing infants exhibited more phasic muscle responses than high-risk infants.
- High-risk infants showed more tonic activity or no muscle response.
- Both groups had similar center of pressure measures and onset latencies, with typically developing infants more frequently showing caudal-cephalad recruitment patterns.
Conclusions:
- Postural development in high-risk infants with motor delays is complex.
- While some postural control elements are appropriate, their frequency is lower in high-risk infants.
- High-risk infants demonstrate immature, but normal, muscle activity sequencing, such as cephalocaudal patterns.
Abstract:
This study examined spatial and temporal organization of muscle activity in response to seated forward platform perturbations in typically developing (TD) infants and in infants at risk for ongoing neuromotor delays. Twelve high-risk (HR) infants (six males, six females) and 12 TD infants (nine males, three females) aged 8 to 10 months (corrected for prematurity), who were all independent sitters, participated in this study. Surface electromyograms recorded muscle responses to forward perturbation in the neck, trunk, and leg (6cm amplitude, 12cm/s). Center of pressure measures were also recorded. The TD infants demonstrated significantly more phasic responses than the HR infants, who had more trials with tonic activity and more trials with no burst of muscle activity (Mann-Whitney U test, two-tailed, p=0.006). The TD infants demonstrated caudalcephalo, directionally appropriate recruitment patterns more often than the HR infants. There were some similarities between the two groups, with no significant difference between any of the center of pressure measures or onset latencies. Results suggest that postural development in HR infants with motor delays is complex. Some elements of seated postural control appear to be developmentally appropriate, e.g. presence of phasic activity in directionally appropriate muscles sequenced in a caudalcephalo pattern. However, frequency of these age appropriate responses was significantly lower in HR infants, who demonstrated many normal, albeit immature, responses, such as cephalocaudally sequenced muscle activity.
