SLIGHTLY SPREAD FINGERS ON A HAND HELD AT 90º TO THE LINE OF INTENDED FORCE PRODUCTION PRODUCES THE MOST FORCE

Marinho, D. A., Barbosa, T. M., Reis, V. M., Vilas-Boas, J. P., Alves, F. B., Kjendlie, P. L., Rouboa, A. I., & Silva, A. J. (2009). The effect of finger spread on the propulsive force production in swimming. ** ACSM 56th Annual Meeting, Seattle, Washington. ** Presentation number 599.

This study determined the effect of finger spread on the propulsive force production in a swimmer's hand 3-D model using computational fluid dynamics. A 3-D domain was created to simulate the fluid flow around three models of a swimmer's hand, according to different finger spreads: fingers close together, fingers with a small distance spread (0.32 cm), and fingers with a large distance spread (0.64 cm). Models were created by computer tomography scans of a male swimmer's hand. The domain was meshed with a hybrid mesh. Numerical simulations for the computational steady domain were calculated in the three dimensions. The governing system of equations considered was the incompressible Reynolds averaged Navier-Stokes equations with the standard k-epsilon model. Pitch angles of hand models of 0º, 30º, 60º, and 90º, with a sweepback angle of 0º (thumb as the leading edge) in a simulated fluid flow of 2.0 m/s were used for the calculations. The measured forces on the three hand models were divided into drag and lift coefficients.

The model with little distance between fingers presented higher values of drag coefficient than the models with the fingers closed and fingers with the large distance spread. The lift coefficient values changed little between the three models for any given pitch angle. The coefficient of drag increased incrementally as the angle of pitch approached 90º.

**Implication**. Slightly spread fingers could allow the hand to create more propulsive force during swimming than wide or no finger spread. This effect is heightened, the closer the hand is held at 90º to the line of intended force production.

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