title: Inter- and intra-lower limb joint coordination of non-expert classical ballet dancers during tiptoe standing.
abstract: The main objective of this study was to compare ballet dancers' and non-dancers' joint coordination during tiptoe standing. Nine female non-expert ballet dancers and nine female non-dancers were asked to perform heel-toe and tiptoe standing for approximately 30s, during which the center of pressure (COP) and kinematic data from the metatarsophalangeal, ankle, knee, and hip joints were measured. Principal component analysis was performed on the angular displacements to determine joint coordination. The weighting vectors suggested that dancers' ankle and knee joints fluctuated in-phase in the anteroposterior direction, whereas all combinations of adjacent joints had anti-phase coordination for non-dancers. In addition, there was a significant difference in the intra-joint coordination pattern between groups. In particular, dancers' metatarsophalangeal (MP) and ankle joints tended to sway to the left-front or right-rear. However, there were no differences between the groups in the path length or rectangular COP. These results suggest that dancers maintained quiet postures via a decrease in the mechanical degree of freedom and that postural expertise may not be determined from a traditional COP analysis, even during unstable tiptoe standing. This in-phase coordination, which has an arch-like configuration, could be characteristic of dancers' lithe legs.
authors.affiliation: Research Fellow of the Japan Society for the Promotion of Science, Japan; Laboratory of Neurophysiology, Graduate School of Human and Environmental Studies, Kyoto University, Kyoto 606-8501, Japan.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Tanabe
authors.affiliation: Research Fellow of the Japan Society for the Promotion of Science, Japan; Laboratory of Neurophysiology, Graduate School of Human and Environmental Studies, Kyoto University, Kyoto 606-8501, Japan.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Fujii
authors.affiliation: Laboratory of Neurophysiology, Graduate School of Human and Environmental Studies, Kyoto University, Kyoto 606-8501, Japan. Electronic address: kouzaki.motoki.4x@kyoto-u.ac.jp.
authors.forename: Motoki
authors.initials: M
authors.lastname: Kouzaki
mesh_terms: D000293:Adolescent; D000843:Ankle Joint / Q000502:physiology; D054874:Athletic Performance / Q000502:physiology; D003615:Dancing / Q000502:physiology*; D004954:Esthetics; D005260:Female; D006621:Hip Joint / Q000502:physiology; D006801:Humans; D007596:Joints / Q000502:physiology*; D007719:Knee Joint / Q000502:physiology; D008683:Metatarsophalangeal Joint / Q000502:physiology; D004856:Postural Balance / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D011214:Practice, Psychological; D011597:Psychomotor Performance / Q000502:physiology*; D016474:Weight-Bearing / Q000502:physiology; D055815:Young Adult
keywords: Center of pressure; Coherence spectrum; Principal component analysis