title: Hydrodynamic analysis of different finger positions in swimming: a computational fluid dynamics approach.
abstract: The aim of this research was to numerically clarify the effect of finger spreading and thumb abduction on the hydrodynamic force generated by the hand and forearm during swimming. A computational fluid dynamics (CFD) analysis of a realistic hand and forearm model obtained using a computer tomography scanner was conducted. A mean flow speed of 2 m · s(-1) was used to analyze the possible combinations of three finger positions (grouped, partially spread, totally spread), three thumb positions (adducted, partially abducted, totally abducted), three angles of attack (a = 0°, 45°, 90°), and four sweepback angles (y = 0°, 90°, 180°, 270°) to yield a total of 108 simulated situations. The values of the drag coefficient were observed to increase with the angle of attack for all sweepback angles and finger and thumb positions. For y = 0° and 180°, the model with the thumb adducted and with the little finger spread presented higher drag coefficient values for a = 45° and 90°. Lift coefficient values were observed to be very low at a = 0° and 90° for all of the sweepback angles and finger and thumb positions studied, although very similar values are obtained at a = 45°. For y = 0° and 180°, the effect of finger and thumb positions appears to be much most distinct, indicating that having the thumb slightly abducted and the fingers grouped is a preferable position at y = 180°, whereas at y = 0°, having the thumb adducted and fingers slightly spread yielded higher lift values. Results show that finger and thumb positioning in swimming is a determinant of the propulsive force produced during swimming; indeed, this force is dependent on the direction of the flow over the hand and forearm, which changes across the arm's stroke.
authors.affiliation: Faculty of Sport, CIFI2D, and Porto Biomechanics Laboratory (LABIOMEP), University of Porto, Porto, Portugal.
authors.forename: João Paulo
authors.initials: JP
authors.lastname: Vilas-Boas
authors.forename: Rui J
authors.initials: RJ
authors.lastname: Ramos
authors.forename: Ricardo J
authors.initials: RJ
authors.lastname: Fernandes
authors.forename: António J
authors.initials: AJ
authors.lastname: Silva
authors.forename: Abel I
authors.initials: AI
authors.lastname: Rouboa
authors.forename: Leandro
authors.initials: L
authors.lastname: Machado
authors.forename: Tiago M
authors.initials: TM
authors.lastname: Barbosa
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Marinho
mesh_terms: D000328:Adult; D054874:Athletic Performance / Q000502:physiology*; D005385:Fingers / Q000502:physiology*; D005542:Forearm / Q000502:physiology; D006801:Humans; D057446:Hydrodynamics; D008954:Models, Biological; D013550:Swimming / Q000502:physiology*; D013933:Thumb / Q000502:physiology