END POINT CONTROL IN A MULTI-JOINT DANCE MOVEMENT : ANALYSIS BETWEEN GROUPS OF DIFFERING SKILL LEVELS

INTRODUCTION Variation in motion between groups of dancers using a commonly performed movement (arabesque) involving coordination of postural control with upper and lower extremity multi-joint movement is presented. Quantitative measurements of “smoothness” and variability were employed in order to evaluate how the control of the arabesque movement varied with increasing skill levels and learning. A number of researchers (Nelson 1983; Hogan 1988; Hreljac 1993) have quantified the “smoothness” of movement using the mean squared magnitude of Jerk – where Jerk is defined as the third derivative of position, or rate of change of acceleration. The value of the Jerk Cost function (1), where T and r are defined as total movement time and limb position vector respectively, will minimised when producing the smoothest movement possible. Normalised Jerk (2) (Kitazawa et al. 1993) is a unit free dependent variable utilised for comparing movement during the acceleration phases of the arabesque.