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Development of postural control--differences between ventral and dorsal muscles?
M Hadders-Algra1, E Brogren, H Forssberg
1Department of Woman and Child Health, Karolinska Institute, Stockholm, Sweden. m.hadders-algra@med.rug.nl
Insights
Infants develop direction-specific postural control synergies early on. Muscle activation patterns refine with age, with dorsal extensors maturing before ventral flexors, aiding upright locomotion development.
Area of Science:
- Developmental motor control
- Neuroscience
- Human movement science
Background:
- Postural control relies on direction-specific muscle synergies.
- Early postural development in infants involves adaptable muscle activation patterns.
- Understanding developmental changes in postural control is crucial for assessing motor milestones.
Purpose of the Study:
- To investigate the developmental trajectory of postural control synergies in infants.
- To identify age-related changes in muscle activation patterns during postural adjustments.
- To compare the development of extensor and flexor muscle synergies.
Main Methods:
- Observational study of muscle activation patterns in sitting infants.
- Analysis of direction-specific muscle synergies during postural sway.
- Longitudinal assessment of postural control development from 5-6 months to 3 years.
Main Results:
- Direction-specific muscle activation patterns are present in infants as young as 5-6 months.
- Muscle activation variability decreases with age, with refined synergies emerging around 9-10 months.
- Dorsal extensor synergies develop earlier than ventral flexor synergies, supporting standing and walking.
- A 'fixed' extensor synergy is prominent from 9 months to 3 years, later dissolving.
- Flexor synergies demonstrate greater flexibility than extensor synergies.
Conclusions:
- Infant postural control develops through progressive refinement of direction-specific muscle synergies.
- The maturation sequence of extensor and flexor synergies influences the development of upright locomotion.
- Differences in stability limits and supraspinal modulation may explain varying flexibility between extensor and flexor synergies.
Abstract:
Postural control is organized in basic, direction specific synergies which can be adapted to task-related conditions. Studies on the development of postural adjustments in young sitting children revealed that largely variable, direction specific muscle activation patterns are already present in 5-6 month old children not able to sit without support. With increasing age, the variation in muscle activation patterns decreases, resulting in a selection of the most complete patterns of synergist activation at 9-10 months of age. The synergy of the dorsal extensor muscles (during a forward sway of the body) develops faster than the synergy of the ventral flexors (during backward body-sway). A 'fixed' extensor synergy is prominently present between 9 months and 3 years, i.e. during the period when standing and walking abilities develop. With increasing age the 'fixed' extensor synergy gradually dissolves. The flexor synergy shows a larger flexibility than the extensor synergy, a difference which can be attributed to differences in stability limits and differences in the degree of supraspinal modulation.