Updating process of internal models of action as assessed from motor and postural strategies in children.

The objective of this study was to investigate the updating process of internal models of action in children and young adults, through the postural and motor strategies adopted in simple tasks, namely sit-to-stand (STS) and back-to-sit (BTS). To this end, 11 healthy children from 7 to 10years (latest stage of childhood) and 12 healthy adults participated in the experiment. The STS and BTS tasks were performed with horizontal support surface and support surface tilted 10° to the right or forward in order to investigate the immediate adaptation of the internal representations of the movement. Movement variables that included the durations of STS and BTS and the amplitudes of the trunk movement were computed. Postural characteristics were also considered during the transition from STS to BTS, including the trunk orientation and the head stabilization strategies. Despite certain similarities with adults, especially in terms of the asymmetry of the performance times for the two tasks (STS vs. BTS) and the partial movement adaptations, the children were less able than adults to adapt both postural and movement controls to the new support conditions. Thus, it appears that the updating of internal models of action is a process that matures slowly throughout ontogenesis.