Athletic skill level is reflected in body sway: a test case for accelometry in combination with stochastic dynamics.

Recent studies on postural control have shown that the variability of body sway during quiet standing may provide valuable information to characterize changes in postural control due to age, pathology, skill and task. The aim of the present study was to determine - as spade work for possible clinical applications - whether body sway measured with a three-axial accelerometer at the trunk can differentiate between three healthy young populations that differ in athletic skill level. The three groups in question (group size: n=22) consisted of regular bachelor students, physical education students and physical education students specialized in gymnastics. Data were recorded during tandem stance with eyes open or closed and while standing on foam. The acceleration time-series were analysed in anteriorposterior and mediolateral direction. Differences in postural control were quantified in terms of variability, spectral properties and stochastic dynamical measures, i.c., regularity (sample entropy, long-range correlations) and local stability (largest Lyapunov exponent). The results were clear-cut. Standing with eyes closed and on foam increased variability. Compared to standing with eyes open, standing with eyes closed resulted in less regular sway patterns but with greater local stability, whereas standing on foam had an opposite effect. With greater gymnastic skills, acceleration time-series were less variable, less regular and more stable. These results imply that quantifying the stochastic-dynamical structure of postural sway using ambulant accelerometry may provide a useful diagnostic tool.