Dissimilarities of the demi-plié movement trajectory in its different roles in classical ballet

Abstract

ABSTRACT Demi-plié is a coordinated dance movement involving knees bent while keeping hips turned out and heels grounded. It consists of descending and ascending phases, the latter often preparing for the next move. Task goals may influence its trajectory. Ten classical dancers (eight females, two males), aged 20–45 years old performed demi-plié itself and prior to pirouette en dehors, relevé, sauté, and sissonne fermée de côté. Lower limb and hip trajectory data were collected through a motion capture system. Time-series data were aligned across all conditions using a dynamic time warping algorithm. The Euclidean distance measured the hip trajectory between each ballet movement, providing a continuous dissimilarity function over time. Descriptive analysis focused on each participant’s maximum dissimilarity values across conditions. Results showed maximum hip trajectory differences of 40% for demi-plié before sauté, 30% before sissonne, 20% before relevé, and 10% before pirouette. Dissimilarities began in the descending phase of the demi-plié. ANOVAs for repeated measures and Bonferroni’s post-hoc showed that the standard deviation of dissimilarity had the largest effect size for the demi-plié – demi-plié before sauté, and the smallest for the demi-plié – demi-plié before pirouette. Demi-plié prior to jumps demands plyometric forces and has open-loop motor planning, requiring acceleration, whereas demi-plié is closed-loop, relying on proprioceptive updating.