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Postural adjustments during spontaneous and goal-directed arm movements in the first half year of life
I B van der Fits1, A W Klip, L A van Eykern
1Department of Medical Physiology, University of Groningen, Developmental Neurology, The Netherlands.
Insights
Infant postural control develops significantly with age, showing organized muscle activity during reaching but not spontaneous movements. Postural adjustments decrease but become more organized as infants mature.
Area of Science:
- Developmental neuroscience
- Motor control
- Infant biomechanics
Background:
- Postural control is crucial for infant development.
- Understanding early motor development informs interventions.
Purpose of the Study:
- To investigate the development of postural control during arm movements in infants.
- To differentiate postural activity during goal-directed vs. spontaneous arm movements.
Main Methods:
- Simultaneous recording of video data and surface electromyography (EMG) of multiple muscle groups.
- Assessment of healthy infants at 3, 4, 5, and 6 months, and a separate group aged 1-3 months.
- Analysis of postural adjustments in various lying and sitting positions.
Main Results:
- High postural activity accompanied both spontaneous and goal-directed arm movements before successful reaching (4-5 months).
- Goal-directed movements showed specific neck muscle activation and directional organization, absent in spontaneous movements.
- Postural activity decreased with age and reaching ability but became more organized.
Conclusions:
- Infants exhibit significant postural adjustments even before independent reaching.
- Development involves a transition from generalized to more organized postural control.
- Body position influences postural adjustments during reaching in infants.
Abstract:
We studied the development of postural control during goal-directed reaching and spontaneous arm movements in early infancy. Two groups of infants participated. The first group consisted of 10 healthy infants, who were assessed four times at the ages of 3, 4, 5 and 6 months. Each assessment consisted of simultaneous recording of video-data and surface EMGs of arm, neck, trunk, and leg muscles in various lying and sitting positions. Additionally, postural adjustments during spontaneous arm movements were studied in a second group of five infants aged 1-3 months. Already before the onset of successful reaching, which occurred at 4 5 months, both spontaneous and goal-directed arm movements were accompanied by a high amount of postural activity. During the goal-directed arm movements a preference for neck muscle activation and a direction specific organisation (dorsal postural muscles activated before the ventral antagonists) prevailed, whereas during spontaneous arm movements such a specific postural organisation was absent. With increasing age and concurrent with successful reaching, the amount of postural activity decreased. Still, the persisting postural activity continued to become more organised with increasing age. Position affected the postural adjustments accompanying goal-directed arm movements at all ages.