Development of postural adjustments in sitting position during the first half year of life

Abstract

Little is known about the development of postural adjustments during early ontogeny. We examined postural adjustments due to sudden perturbations during sitting in 40 healthy term infants (28 males, 12 females) assessed in groups of eight at 1, 2, 3, 4, and 5 months of age. Surface electromyograms of neck, trunk, and leg muscles were recorded while the infants were exposed to a random series of horizontal forward and backward displacements of the surface of support. Video recordings of spontaneous motor behaviour were analyzed. For part of the analyses, previously collected data on 26 infants aged 6 to 10 months were included. In general, postural adjustments at all ages were direction specific and showed large variation. Within the variation developmental changes could be observed, revealing a transient decrease in postural activity at 3 months of age. After this transition, direction-specific postural activity was correlated with spontaneous motor behaviour. This was true, in particular, for dorsal postural activity. The clinical relevance of these findings is discussed.

Postural adjustments and reaching in 4- and 6-month-old infants: an EMG and kinematical study

“…The more precise deWnition resulted in substantially lower rates of direction-speciWcity. The studies of Hedberg et al (2004Hedberg et al ( , 2005 indicated that direction-speciWcitydeWned in the same precise manner as in the current study-is virtually always present in young sitting infants when their balance is grossly perturbed by a sudden movement of the support surface. The postural threat during reaching while lying supine or while sitting supported is considerably less.…”

Equilíbrio postural: investigação com crianças, adultos e idosos

“…O controle postural ou a preferência por formas específicas de recrutamento da estabilidade dependem da idade dos indivíduos e da natureza do desafio postural (HEDBERG et al, 2005;NU-NES;FONSECA;SCHEICHER, 2013;CIGNETTI et al, 2013). Crianças em idade escolar, por exemplo, não mostram uma preferência clara para a manutenção da estabilidade (CIGNETTI et al, 2013).…”

Trunk and respiratory motor control in typically developing children and its implications in children with chronic spinal cord injury.

“…However, they found no organized patterns of muscle activities and suggested that neonates lack the ability to control their neck not only due to lack of muscle strength but also due to lack of coordinated muscle activities. Other studies have focused on the development of muscle synergies during reactive trunk control (following external perturbations) and muscle synergies during anticipatory balance (reaching movements) (Hedberg, Carlberg, Forssberg, & Algra, 2005;Hedberg, Forssberg, & Hadders-Algra, 2004). These studies suggested that infants as young as 1 month could generate direction specific postural adjustment in the neck and the trunk muscles during external perturbation.…”

“…the level responsible for generating muscle synergies. However, these muscle synergies or adjustments were uncoordinated (Hedberg et al, 2005;Hedberg et al, 2004; M. Woollacott, Debu, & Mowatt, 1987). Three months is considered to be the age of functional transition, because, at this age, infants start to show spontaneous motor behavior related to postural activities.…”

“…Three months is considered to be the age of functional transition, because, at this age, infants start to show spontaneous motor behavior related to postural activities. The presence of the direction specific synergies among neonates suggests that postural adjustment is innate and is present before independent sitting is achieved (Hedberg et al, 2005).…”