Transient body sway characteristics during single-leg quiet stance in ballet dancers and young adults

This study explored transient characteristics of body sway during single-leg quiet stance in young ballet dancers (n = 41) and young healthy adults (n = 58). We compared the groups in terms of center of pressure (CoP) parameters (CoP velocity and amplitude, averaged across the duration of the 30-s trial), and the transient characteristics of the corresponding parameters, which were expressed as relative differences between the 1st and 2nd, and the 1st and 3rd 10-second interval within the trial (DIF_21 and DIF_31, respectively). Ballet dancers exhibited superior quiet stance postural control (2/5 parameters), as well as different transient behavior (3/5 parameters for DIF_21, and none for DIF_31). Specifically, the ballet dancers reduced body sway more during the 2nd interval, resulting in lower DIF_21 for CoP velocity (total and anterior-posterior) and CoP amplitude (medial-lateral) (effect size = 0.42-0.54). The correlations between individual CoP parameters and the corresponding DIF_21 and DIF_31 were very small or trivial (r < 0.15), suggesting that the outcomes pertaining to transient characteristic of body sway within the trial (specifically DIF_21) could represent additional information regarding the postural control during quiet stance. Future studies or even re-analyses of existing data are desired to reveal whether the measures of transient characteristics of body sway have any additional clinical utility compared to traditional whole-trial analyses.