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Practice modifies the developing automatic postural response
1School of Rehabilitation Sciences, Faculty of Health Sciences, University of Ottawa, Ontario, Canada.
Insights
Infant experience with postural tasks improves automatic postural responses. Training increased muscle activation probability and the number of muscles used, but not response speed.
Area of Science:
- Developmental motor control
- Infant motor development
- Postural control mechanisms
Background:
- Automatic postural responses are crucial for maintaining balance.
- Understanding how experience shapes these responses in infants is key to developmental research.
- Previous research has not fully elucidated the impact of specific postural task experience on infant postural control components.
Purpose of the Study:
- To investigate how experience with a specific postural task affects key components of automatic postural responses in infants.
- To analyze the probability of muscle activation, the number of muscles activated, and their onset latencies.
- To determine if targeted training enhances these automatic postural responses.
Main Methods:
- 15 infants (36-48 weeks) performed a postural task involving platform perturbations (forward/backward sway).
- A training group received intensive perturbation training between two test sessions; a control group did not.
- Electromyograms of leg and trunk muscles were recorded to analyze muscle activation probability, number of muscles activated, and onset latencies.
Main Results:
- The training group showed significantly increased probability of activating appropriate postural muscles (tibialis anterior, quadriceps, abdominals for backward sway; gastrocnemius for forward sway).
- The number of functionally appropriate postural muscles activated per trial also increased in the training group.
- No significant changes were observed in mean muscle onset latencies or antagonist coactivation for either group.
Conclusions:
- Experience with a postural task selectively enhances specific parameters of the automatic postural response in developing infants.
- Targeted training can improve the recruitment and coordination of postural muscles.
- Developmental plasticity in automatic postural control is demonstrated through task-specific experience.
Abstract:
The purpose of this study was to examine effects of experience with a postural task on components of the automatic postural response including: (1) probability of activation of functionally appropriate postural muscles; (2) number of functionally appropriate postural muscles activated; and (3) onset latencies of functionally appropriate postural muscles in infants. Infants (n=15; age 36-48 weeks old) able to pull themselves into a standing position but not able to walk independently were tested using a postural task requiring the infant to stand and balance, with support, following a forward or backward movement of the support surface (platform perturbation). Infants were tested twice at 5-day intervals. One-half of the infants, the training group, were given intense platform perturbation training on the days between test sessions. Infants in the second group were also brought into the laboratory on the days between test sessions but were not exposed to platform perturbations during those days. Electromyograms of six leg and trunk muscles were recorded during test sessions to provide muscle onset latencies, probability of muscle activation data, and the number of postural muscles activated following a perturbation. Training infants demonstrated significant increases in probability of activating functionally appropriate muscles with tibialis anterior, quadriceps, and abdominal muscles activated in response to backward sway and gastrocnemius muscle in response to forward sway. The number of functionally appropriate postural muscles activated in a single trial also increased in the training group. There were no significant changes in mean postural muscle onset latencies or number of trials with antagonist muscle coactivation for either training or control groups. These findings suggest that during development selective parameters of the automatic postural response are affected by experience with the postural task.