Reliability of assessing ballet dancers’ postural stability in the unshod and the en pointe relevé position with a smartphone application

Purpose. this study aimed to verify the reliability of estimating ballet dancers’ postural stability during the unshod and the en pointe relevé position with a smartphone application Methods. the participants (13 ballet dancers, 22.4 ± 2.5 years of age) were tested in the unshod and the en pointe relevé position (YMED Balance test application, smartphone secured at the L5 level for centre of mass approximation, 10 trials for each condition, 10 seconds per trial, 2-minute intertrial break, arms relaxed at bodyside, gaze fixated at an eye-level target, preferred feet width and orientation). Paired t-tests examined the inter-condition differences. relative (intraclass correlation coefficient, Icc) and absolute (standard error of measurement, SEM, SEM%) reliability indices (for accumulated and paired trials) were computed for each condition (SPSS software v. 26.0, p < 0.05). Results. the total balance score and all centre of mass spatial measures indicated worse postural stability in the en pointe condition ( p < 0.05), with no significant temporal differences ( p > 0.05). the total body balance score was the most reliable measure (good to excellent Iccs, low to moderate SEM%) with a minimum of 8 trials ensuring reliability in both the unshod and the en pointe relevé positions. Conclusions. taken a minimum of 8 trials and the measure of total balance score, we may obtain a reliable estimation of ballet dancers’ postural stability in the unshod and the en pointe relevé position by using the YMED Balance test smartphone application.