DEVELOPMENT OF POSTURAL CONTROL - DIFFERENCES BETWEEN VENTRAL AND DORSAL MUSCLES

Postural control is organized in basic, direction specific synergies w hich can be adapted to task-related conditions. Studies on the develop ment of postural adjustments in young sitting children revealed that l argely variable, direction specific muscle activation patterns are alr eady present in 5-6 month old children not able to sit without support . With increasing age, the variation in muscle activation patterns dec reases, resulting in a selection of the most complete patterns of syne rgist activation at 9-10 months of age. The synergy of the dorsal exte nsor muscles (during a forward sway of the body) develops faster than the synergy of the ventral flexors (during backward body-sway). A 'fix ed' extensor synergy is prominently present between 9 months and 3 yea rs, 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 syne rgy, a difference which can be attributed to differences in stability limits and differences in the degree of supraspinal modulation. (C) 19 98 Elsevier Science Ltd. All rights reserved.