SLIGHTLY SPREAD FINGERS PRODUCES GREATEST HAND DRAG-FORCE

Marinho, D. A., Barbosa, T. M., Reis, V. M., Kjndlie, P. L., Alves, F. B., Vilas-Boas, J. P., Machado, L., Silva, A. J., & Rouboa, A. I. (2010). Swimming propulsion forces are enhanced by a small finger spread. ** Journal of Applied Biomechanics, 26, ** 87-92.

This study investigated the effect of finger spread on the propulsive force production in swimming using computational fluid dynamics. Computer tomography scans of an Olympic swimmer's hand were conducted. This procedure involved three models of the hand with differing finger spreads: fingers closed together (no spread), fingers with a small (0.32 cm) spread, and fingers with large (0.64 cm) spread. Steady-state computational fluid dynamics analyses were performed using the Fluent code. The measured forces on the hand models were compartmentalized into drag and lift coefficients. Angles of attack of 0°, 15°, 30°, 45°, 60°, 75°, and 90°, with a sweep back angle of 0°, were used for the calculations.

The model with a small spread between fingers presented higher drag coefficient values than did the models with fingers closed and fingers with a large spread. The drag coefficient was highest values for an attack angle of 90° in the three hand models. The lift coefficient resembled a sinusoidal curve across the attack angle. The values for the lift coefficient presented few differences among the three models, for a given attack angle.

**Implication**. The fingers slightly spread allows the hand to create more propulsive force than when fingers closed.