Characteristic relationship between the centre of pressure and the centre of mass during quiet standing in female ballet dancers

The purpose of this study was to examine the characteristics of centre of pressure (COP) and centre of mass (COM) fluctuations in ballet dancers standing quietly. Ten healthy young women performing classic ballet dance as recreational exercise (dancer group) and 10 healthy non-ballet dancers young women who were not ballet dancers (control group) participated in this study. Participants were instructed to maintain three standing positions as steadily as possible (two-legged stance, one-legged stance, and tiptoe stance) with their eyes open. The COP and COM displacements, the distance between COP and COM displacements (COP-COM distance), and the 95% confidence ellipse areas of the COP and COM in the anterior-posterior and mediolateral directions were calculated to assess postural stability. The mean absolute value of the COP-COM distance and the absolute value of the mean COP-COM distance in each direction during one-legged standing in the dancer group were shorter than these values in the control group. These results suggest that the COP fluctuates more closely and evenly, in both directions, around the COM during one-legged standing in athletes with superior postural stability, which would provide a basis for feedback training using both COP and COM displacements for improving static balance.