Measuring a pirouette: examining the validity of biomechanical measures for double pirouette performances.

Pirouette performance has been widely analysed biomechanically, with performance quantified by disparate measures. Therefore, this study examined the criterion validity of biomechanical measures in relation to expert ratings of balanced pirouette performance, and secondarily, dancers' subjective performance evaluations. Forty-nine dancers performed a collective 353 double pirouettes recorded with 3D motion capture. Dancers rated their own performance on a scale from 1 to 10. Following, kinematic data were used to create stick-figure videos, which three experts rated for balance performance on a scale of 1 to 6. Expert rating reliability was assessed with an Intraclass Correlation (ICC). Correlations were calculated between 16 kinematic measures and (1) expert observers' ratings of balance performance and (2) dancers' subjective ratings of overall performance. Overall, there was strong agreement among experts (ICC = 0.92). Dancer and expert ratings most strongly correlated with the pathlength of the supporting foot over the whole pirouette (rs-dancer = -0.59, rs-expert = -0.65). Interestingly, total degrees of trunk rotation-a common field measure-did not significantly relate to expert or dancer ratings. Rather, supporting foot displacement was the strongest field-based correlate (rs-dancer = -0.50, rs-expert = -0.50). These findings thus provide a basis for selecting kinematic measures that reflect practitioner evaluations and underlying biomechanical principles of pirouette performance.