Dual-task effect on postural control in high-level competitive dancers.

We investigated balance in 33 competitive dancers (17 females, 16 males) and 22 controls (17 females, 5 males) (age 16-27 years) on a force plate in two conditions: single task (quiet stance) and dual task (with a concurrent mental task). Balance was evaluated using centre-of-pressure shift (sway) variability, mean speed, frequency, and sample entropy. The effect of the dual task in the medio-lateral plane was comparable in both groups, decreasing sway variability (P < 0.05) and increasing mean speed (P < 0.001), frequency, and sample entropy (P < 0.001), showing that the participants effectively increased the level of automaticity. In the antero-posterior plane, the dual task also increased sway frequency and sample entropy (P < 0.01) in dancers without affecting their standing performance. In contrast, postural control in non-dancers was vulnerable to reduced cognitive investment, which adversely interfered with baseline performance. There were very high correlations between sway sample entropy and frequency in each group, plane, and task (r = 0.92-0.98, P < 0.001), indicating that both parameters may measure the same characteristic of postural control and that higher sway frequency may play an important role in protecting stability in dual tasking. The postural control of dancers and non-dancers appears to be similar, although dancing seems to facilitate the increased level of automatic control in the antero-posterior plane.