SLIGHTLY SPREAD FINGERS AND VARIED THUMB POSITIONS BEST FOR THE HANDS
Marinho, D. A., Barbosa, T. M., Kjendlie, P. L., Reis, V. M., Vilas-Boas, J. P., Machado, L., Rouboa, A. I., & Silva, A. J. (2010). Computational fluid dynamics applied competitive swimming: The role of finger position. A paper presented at the XIth International Symposium for Biomechanics and Medicine in Swimming, Oslo, June 16–19, 2010.
The aim of this study was to use computational fluid dynamics to present the hydrodynamic characteristics of a true model of a swimmer’s hand with different finger positions. Scans of the right hand of a male elite swimmer were obtained using a computer tomography scanner. The hand was scanned with fully abducted (68º), partially abducted (30º), and adducted thumb positions. Scans also were made with fingers closed together, with a small spread (0.32 cm), and with large spread (0.64 cm). Steady-state computational fluid dynamics analyses were performed. The measured forces on the hand models were decomposed into drag and lift coefficients. Attack angles of hand models of 0º, 45º, and 90º, with a sweep back angle of 0º were used.
The position with the thumb adducted presented slightly higher drag-coefficient values compared to thumb abducted positions. The position with the thumb fully abducted presented higher lift-coefficient values at attack angles of 0º and 45º. The model with little distance between fingers presented higher drag-coefficient values than the models with fingers closed and with a large distance spread. Lift coefficient values showed little differences between the attack angles.
Implication. For hand positions in which the lift force can play an important role (e.g,. insweep phases), the abduction of the thumb (spreading it away from the palm) may be better, whereas at higher angles of attack, in which the drag force is dominant, the adduction of the thumb (holding it close to the hand) may be preferable. Moreover, these thumb positions should be associated with the fingers slightly spread, allowing the hand to create more propulsive force during swimming.
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