Development of postural control--differences between ventral and dorsal muscles?
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.
Hadders-Algra
M
M
Department of Woman and Child Health, Karolinska Institute, Stockholm, Sweden. m.hadders-algra@med.rug.nl
Brogren
E
E
Forssberg
H
H
D006801:Humans; D024510:Muscle Development; D018482:Muscle, Skeletal / Q000254:growth & development* / Q000294:innervation / Q000502:physiology*; D011187:Posture / Q000502:physiology*