Swimming propulsion forces are enhanced by a small finger spread

Department of Sport Sciences, University of Beira Interior, Covilhã, Portugal.
Journal of applied biomechanics (Impact Factor: 0.98). 02/2010; 26(1):87-92.
Source: PubMed


The main aim of this study was to investigate the effect of finger spread on the propulsive force production in swimming using computational fluid dynamics. Computer tomography scans of an Olympic swimmer 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 decomposed into drag and lift coefficients. For hand models, angles of attack of 0 degrees, 15 degrees, 30 degrees, 45 degrees, 60 degrees, 75 degrees, and 90 degrees, with a sweep back angle of 0 degrees, were used for the calculations. The results showed that the model with a small spread between fingers presented higher values of drag coefficient than did the models with fingers closed and fingers with a large spread. One can note that the drag coefficient presented the highest values for an attack angle of 90 degrees 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. These results suggested that fingers slightly spread could allow the hand to create more propulsive force during swimming.

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    • "In the front-crawl technique, the majority of the propulsive force is generated by the swimmer's arm action (Berger, de Groot, & Hollander, 1995; Deschodt, Arsac, & Rouard, 1999). Most studies that have attempted to estimate the amount of propulsion generated by the arms have focussed on the hand (Gourgoulis et al., 2008; Marinho et al., 2010) or the hand together with the forearm (Berger, Hollander, & de Groot, 1999; Bixler & Riewald, 2002; Rouboa, Silva, Leal, Rocha, & Alves, 2006). The motion of the upper arm is not generally thought to contribute to propulsion in able-bodied front-crawl swimming. "
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    • "can increase about 10% by the optimization. With the similar approach using Fluent® in a steady state condition, flows around a hand of an Olympic swimmer were analyzed with different thumb positions (Marinho et al., 2009) and with different degrees of the small-finger spread (Marinho et al., 2010), Marinho et al. (2011) also analyzed flow around a hand and forearm of an elite swimmer, and Bilinauskaite et al. (2013) investigated the influence of finger position and orientation of hand on drag and lift forces, although no validations were undertaken in these research. As described above, although CFD has been applied to the analysis of flow around a hand, all of them are in steady state condition, except one study (Rouboa et al. 2006). "
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    • "It means that the shape of the hand had different contributions on the drag force during separate underwater phases of front crawl stroke cycle. Likewise, it was summarised that higher drag force values could be reasonable by a hand model with optimal spacing between fingers [10, 12]. According to the current results, it is clear that, in order to increase the drag force contribution throughout the underwater stroke cycle, the shape of the hand should be altered in separate individual phases. "
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