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Goal directed reaching and postural control in supine position in healthy infants
B Fallang1, O D Saugstad, M Hadders-Algra
1Faculty of Health Sciences, Oslo College, Pilestredet 52, 0167, Oslo, Norway. bjorg.fallang@hf.hioslo.no
Insights
Infant reaching and postural control improve significantly between 4 and 6 months. Postural stability increases, while reaching becomes more efficient, indicating developing motor control.
Area of Science:
- Developmental motor control
- Infant biomechanics
- Postural development
Background:
- Reaching and postural control are crucial motor skills that develop throughout infancy.
- Understanding the interplay between these skills provides insight into early motor development.
Purpose of the Study:
- To investigate the developmental changes in reaching kinematics and postural control (center of pressure - COP) in infants.
- To examine the relationship between reaching movements and postural adjustments in the supine position.
Main Methods:
- Kinematic data of goal-directed reaches and ground reaction forces (COP) were collected from 12 healthy infants at 4 and 6 months.
- Analysis focused on movement units (MU), hand path length, and COP displacement in cranial-caudal and medial-lateral directions.
Main Results:
- Postural stability improved from 4 to 6 months, evidenced by decreased medial-lateral COP oscillations.
- Reaching performance enhanced, shown by fewer MUs, shorter hand paths, and longer/more duration in the first MU.
- The relationship between reaching kinematics and COP dynamics shifted, suggesting evolving motor control strategies.
Conclusions:
- Infants demonstrate significant improvements in both reaching and postural control between 4 and 6 months.
- The changing correlation between reaching and postural control indicates a refinement in the subtle control of postural adjustments during reaching movements.
Abstract:
The present study focussed on the development and interaction of reaching and posture in supine position in young infants. The kinematics of goal directed reaches and the concurrent ground reaction forces of the total body centre of pressure (COP) in cranial-caudal and medial-lateral direction were recorded in twelve healthy fullterm infants at 4 and 6 months of age. From eight infants, data were available at both ages. The results indicated that between 4 and 6 months, postural stability during reaching in supine position increased, as the oscillatory COP displacement in the medial-lateral direction decreased significantly with increasing age. Concurrently, reaching performance improved, which was reflected by a decrease in the number of movement units (MU), the length of the displacement-path of the hand and an increase of the length and duration of the first MU. The kinematic data of the reaching movements and the COP data were correlated at both ages, but the nature of the relation changed. At 4 months of age, the number of MU was related to the number of COP oscillations in the cranial-caudal direction, whereas at 6 months the maximum velocity of the hand movement was related to the maximum velocity of COP displacement in cranial-caudal and medial-lateral direction. This change might point to the development of a more subtle control of postural adjustments during reaching movements in supine position.