Twist within a somersault |
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| Affiliation: | 1. Channing Division of Network Medicine, Department of Medicine, Brigham and Women''s Hospital and Harvard Medical School, Boston, Mass;2. Renal Division, Department of Medicine, Brigham and Women''s Hospital and Harvard Medical School, Boston, Mass;3. Department of Epidemiology, Harvard T. H. Chan School of Public Health, Boston, Mass;4. Endocrinology Division, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Mass;5. Division of Adolescent and Transition Medicine, Cincinnati Children''s Hospital Medical Center and University of Cincinnati College of Medicine, Ohio;1. Discipline of Physiotherapy, Faculty of Health, University of Canberra, 11 Kirinari Street, Bruce, ACT 2617, Australia;2. UCRISE, University of Canberra, 11 Kirinari Street, Bruce, ACT 2617, Australia;1. Rockefeller Neuroscience Institute, West Virginia University, USA;2. Program in Human Movement Science, University of North Carolina at Chapel Hill, USA;3. MOTION Science Institute, University of North Carolina at Chapel Hill, USA;4. Department of Exercise and Sport Science, University of North Carolina at Chapel Hill, USA;1. Department of Vascular Surgery and Kidney Transplantation, University Hospital of Strasbourg, Strasbourg, France;2. Groupe Européen de Recherche sur les Prothèses Appliquées à la Chirurgie Vasculaire, Strasbourg, France;3. Department of Anaesthetics, University Hospital of Strasbourg, Strasbourg, France |
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| Abstract: | The twisting somersault is a key skill in diving and gymnastics. The components of twist and somersault are defined with respect to anatomical axes, and combinations of multiples of half rotations of twist and somersault define specific twisting somersault skills. To achieve a twisting somersault skill twist must be continuous; otherwise oscillations in twist while somersaulting may be observed. The posture-dependent inertial properties of the athlete and the initial conditions determine if continuous or oscillating twist is observed. The paper derives equations for the amount of somersault required per half twist, or per twist oscillation, without making assumptions about the relative magnitudes of the moments of inertia. From these equations the skills achievable may be determined. The error associated with the common assumption that the medial and transverse principal moments of inertia are equal is explored. It is concluded that the error grows as the number of twists per somersault decreases, when the medial and transverse moments of inertia diverge, and when the longitudinal moment of inertia approaches either the medial or transverse moment of inertia. Inertial property data for an example athlete are used to illustrate the various rotational states that can occur. |
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| Keywords: | Diving Gymnastics Angular momentum Rotation axis |
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