Feedforward versus feedback control in children and adults subjected to a postural disturbance

Abstract

Any action performed by standing subjects is generally accompanied by compensatory postural activities, which reduce or abolish the postural disturbance generated by the movements and keep the subjects' center of gravity within the supporting base. These postural activities are triggered by either anticipatory and/or feedback-based control processes, depending on the information available and on the behavioral context. To investigate the respective involvement of these two components in postural control during development, we studied the extent to which the postural equilibrium of children (3-to 10-year-olds) and adults was disturbed by the same physical event, an unloading, depending on whether it was initiated by the subject or externally imposed. The subjects were standing on a force platform with their eyes closed, holding a load (5% of their own body weight) in their hands, with arms vertical and forearms horizontal. Two conditions were applied: (1) the subjects voluntarily released the load and (2) the load was unpredictably removed. The unloading resulted in a backward movement of the center of pressure, which was smaller with self-initiated than imposed disturbances in all age groups. This difference varied depending mainly on the age-related changes in the relative amplitude of the self-initiated disturbance, which decreased between 3- to 5-, and 6- to 8-year-olds (who showed no marked postural instability after self-initiated unloading), and increased again in the two older groups (9- to 10-year-olds and adults), in which it also became more consistent It was concluded that feedforward control. becomes more efficient as children grow up, but that its relative contribution to postural control does not show a monotonic pattern of development.

Anticipatory postural adjustments associated with a forward leg raising in children: Effects of age, segmental acceleration and sensory context

“…Two factors may explain this observation: The younger children had a less stable initial posture and/or a lack in cognitive control of the movement. Our results confirmed previous findings indicating that (1) the expression of anticipatory postural adjustments was still developing during mid-childhood and (2) the adult-like pattern was not reached at 8 (Hay and Redon, 1999;McFadyen et al, 2001;Schmitz et al, 2002).…”

“…According to these authors, the feedforward control is fully developed approximately at 7 years old. Hay and Redon (1999) showed that the contribution of the feedforward processes to postural control evolve non-monotonically between 3 and 10 years old. Although postural responses of 6-year-old children were almost similar to those of adults, the feedforward control appeared to be less efficient for the 9-to 10-year-old children.…”

Age differences between children and young adults in the dynamics of dual-task prioritization: Body (balance) versus mind (memory).

“…Similar patterns of motor task prioritization have been observed in older adults (Li et al, 2001;Rapp et al, 2006). Our results also match findings demonstrating developmental phases of temporary overcontrol of posture during childhood (Hay & Redon, 1999;Kirshenbaum, Riach, & Starkes, 2001). Young adults, on the other hand, who showed less body sway than children when balancing on the board, can "afford" to increase their sway under dual-task conditions without risking their balance.…”

“…A potential explanation is that the kinds of resources required to perform the two tasks concurrently originate from different and distinguishable resource pools (Navon & Gopher, 1979) instead of a unique, general-purpose unit or structure (Kahneman, 1973). In this vein, the distinction between feedforward and feedback control of balance proposed by Hay and Redon (1999) could elucidate the processes required when balancing on the stable or moving platform. According to that account, feedforward control comes into play when an individual's own movements generate balance disturbances, and "anticipatory" postural adjustments can be triggered prior to the self-induced disturbance.…”

The Ability to Maintain Static Balance in Younger School Children and Its Relation to the Stability of a Posturographic Surface

“…However, disturbed body balance does not necessarily reflect functioning of the balancing system, but may be also associated with growth-related changes, side effects of taken medicines, or disorders of spatial orientation (Cho and Kamen, 1998;Waśkiewicz, 2002;Kostiukow et al, 2009). According to literature, stabilization of body posture in children being under intensive biological development should be reflected by a decrease in the number body sways and degree of COP displacement (Hay and Redon, 1999).…”