Early development of postural adjustments in standing with and without support

Abstract

This study investigates the early development of postural adjustments during external perturbations in two different standing positions: standing with support and standing without support. The aim of the study was to assess a group of 13 infants four times during the period in life when independent standing is achieved; at 8, 10, 12 and 14 months. However, longitudinal data could be achieved only in four infants. Muscle activations of the neck, hip and ankle were recorded using surface electromyography. Based on earlier studies and controversies, three main issues were addressed: (1) Is direction specificity present before independent standing is established? (2) How do postural adjustments change with increasing age (8-14 months)? (3) Are postural adjustments task-specific in the young child? The results showed that our small sample of infants aged 8 and 10 months, who were not yet able to stand independently, exhibited direction-specific postural adjustments both during standing with and without support, though not consistently during all trials and at all body levels. Therefore, we argue that direction specificity might constitute a prerequisite for the development of independent standing. We also found that the development of postural adjustments in standing with support resembles that of sitting, i.e. great variation in the postural adjustments at early age, and fine-tuning to the situation with increasing age and experience. This, we find that this is in agreement with the proposal that postural control develops through a selection process of the most suitable postural adjustments for the situation from a repertoire of direction-specific postural adjustments. The development of postural adjustments during standing without support is discussed. Additionally, differences in response rates were noted between the two standing positions, indicating that even before independent standing is established, sophisticated sensorimotor integration enables task-specific postural adjustments.

Exploring Task-Specific Independent Standing in 3- to 5-Month-Old Infants

“…In fact, the findings could reflect the continual complex interaction between genetic information and environmental influences that characterize the developmental process, as underlined in the NGST (Hedberg et al, 2007; Ulrich, 2010; Blauw-Hospers et al, 2011). Due to an innate activation of muscles that takes place before independent standing develops (the phase of primary repertoire) (Hadders-Algra, 2000), infants could display postural responses that enable them to stand in the hands of the instructor.…”

“…Accordingly, the findings of increased time-to-stand could be a result of an adaptation to more advanced direction specific adjustment (Hadders-Algra, 2005; Hedberg et al, 2007). This phenomenon has earlier been highlighted in studies focusing on postural control in sitting (Hadders-Algra et al, 1996) and standing with and without support (Hedberg et al, 2007). As Hadders-Algra (2010) highlight: the primary genetic determinations is only the starting point for epigenetic cascades, allowing for abundant interaction with the environment and activity-dependent processes (p. 1825).…”

“…As stated by Hedberg et al (2007), there are methodological challenges associated with studying the development of independent standing, as infants under the age of 9 months per se are not expected to be able to stand independently. In order to explore independent standing, 3–5 months old infants participating in a baby swimming course were recruited to participate in the study.…”

Newly Standing Infants Increase Postural Stability When Performing a Supra-Postural Task

“…[16]. Given that reactive strategies are feedback driven, proper function requires sensory information (detection of the balance threat) to be integrated with the proper motor response within a reasonable time delay [17]–[19]. The sensory integration needed for proper feedback postural control begins to develop early in infancy [20].…”

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

“…Infants between the ages of 5 to 7 months responded with more consistent activation of muscle synergies along with increased tonic activation of agonist and antagonist muscle groups (Hedberg, Schmitz, Forssberg, & Hadders-Algra, 2007; M. Woollacott et al, 1987). After the age of 8 months, infants start to generate more appropriate adjustment patterns as observed in adults (HaddersAlgra, 2000; M. Woollacott et al, 1987).…”