Quantifying ballet technique through turn kinematics for injury assessment

Abstract

The most common turns in ballet, pirouettes and fouettés require precise movement to match proper technique and prevent injury. Variation in knee angle of a dancer's supporting leg during pirouettes of 1-5 rotations was measured using a goniometer for 12 professional and pre-professional ballet dancers. Plié angle saw no significant difference for different numbers of rotations, but the effect of gender was significant: males pliéd at least 20.3 degrees deeper than females. Average knee angle while turning was less than zero for all pirouettes, highlighting dancers' tendency to bend their supporting knee to correct for instability, which may contribute to knee injuries. Knee angle trajectory closely matched a minimum jerk profile, indicating that dancers encode movements in angle coordinates. Knee angle was compared between pirouettes and fouettés using 2 goniometers and aerial video for 3 advanced amateurs. No difference was found in preparation plié or turn angle between turn types. Axis of rotation remained within 0.221 +/- 0.014 meters of starting position during fouettés. Maximum angular velocity of the head was nearly one and a half times that of the body during fouettés. This kinematic definition of ballet technique creates a framework for movement control of a dancer's lower extremities to prevent injury.