Antonia M Zaferiou1, Rand R Wilcox, Jill L McNitt-Gray. 1. USC Biomechanics Research Laboratory, Dep. of Biological Sciences and Biomedical Engineering, University of Southern California, 3616 Trousdale Parkway, AHF-252, Los Angeles, CA 90089, USA. Tel 213-740-7903. zaferiou@alumni.usc.edu.
Abstract
OBJECTIVE: To compare dancers' balance regulation at the whole-body level under increased rotational demands during the turn phase of turns with and without large center-of-mass (CM) translation (i.e., piqué vs pirouette turns). METHODS: Ten dancers performed single and double piqué and pirouette turns while kinematics and reaction forces were measured. During the turn phase, initial CM velocity, vertical alignment of the CM, mean braking force, and moment about the CM were compared across turn conditions using within-subject (Cliff's analog of Wilcoxon-Mann-Whitney test, adjusted for multiple comparisons) and group (sign test) statistical methods. RESULTS: For both single and double turns, the piqué turn phase was initiated with a significantly larger CM velocity towards the base of support than during the pirouette, consistent with the mechanical objectives of the turn. Additionally, during the turn phases of both single and double turns, the CM during the pirouette turns was more vertically aligned with the base of support than it was during the piqué turns. As rotational demand increased in both turns, the reaction forces were regulated in two ways to minimize the CM horizontal velocity as it approached vertical alignment with the base of support. By controlling the braking force and moment applied about the CM early during the turn phase, the potential for the CM to remain vertically aligned with the base of support increased. These findings can assist development of training tools geared towards balance regulation during pirouette and piqué turns.
OBJECTIVE: To compare dancers' balance regulation at the whole-body level under increased rotational demands during the turn phase of turns with and without large center-of-mass (CM) translation (i.e., piqué vs pirouette turns). METHODS: Ten dancers performed single and double piqué and pirouette turns while kinematics and reaction forces were measured. During the turn phase, initial CM velocity, vertical alignment of the CM, mean braking force, and moment about the CM were compared across turn conditions using within-subject (Cliff's analog of Wilcoxon-Mann-Whitney test, adjusted for multiple comparisons) and group (sign test) statistical methods. RESULTS: For both single and double turns, the piqué turn phase was initiated with a significantly larger CM velocity towards the base of support than during the pirouette, consistent with the mechanical objectives of the turn. Additionally, during the turn phases of both single and double turns, the CM during the pirouette turns was more vertically aligned with the base of support than it was during the piqué turns. As rotational demand increased in both turns, the reaction forces were regulated in two ways to minimize the CM horizontal velocity as it approached vertical alignment with the base of support. By controlling the braking force and moment applied about the CM early during the turn phase, the potential for the CM to remain vertically aligned with the base of support increased. These findings can assist development of training tools geared towards balance regulation during pirouette and piqué turns.