Postural control strategies in young adults during dual tasking in different stance positions
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In everything we do, we need to have control over our body’s position in space. Traditionally, postural control is assumed to need few attentional resources that are directed instead to other ongoing tasks. Changes in postural control while conducting a concurrent cognitive task compared to a baseline level of performance is referred to as dual task interference. The aim of this study was to investigate the effect of dual tasking on postural control with the following specific question: Does the type and magnitude of postural control movements depend on the difficulty of concurrent cognitive tasks, the level of difficulty of stance position, or both? Participants performed three different difficulty levels of counting (counting backwards in 1s, 3s and 7s) during two different challenges to postural control (standing with feet hipwidth apart or close together). Data collected consisted of force plate measurements and 3-dimensional motion capture. Analyses focused on Centre of Pressure (CoP) and Principal Component Analysis (PCA), respectively. PCA identified four important categories of movements: postural movements, breathing movements, head movements, and multi-segment movements. Stance position, but not dual tasking affected the CoP measures. In contrast, PCA was capable of detecting significant task effects on principal velocity and principal acceleration, and some task effects on principal movements. Furthermore, there was a tendency for higher order PCs to be more sensitive to changes in task than lower order PCs. The latter, especially ankle and hip movements dominate CoP measures. In conclusion, stance position influenced postural control as indicated by changes in CoP measures, but the latter were not sensitive to cognitive dual tasks. In contrast, PCA clearly distinguished single task from different levels of counting, even from single task to simple backwards counting in 1s, especially with respect to principal velocity and acceleration.