Ribeiro, J., Fernandes, R. J., Machado, L., & Vilas-Boas, J. P. (2011). Hydrodynamic drag characterization of the swimming conventional techniques. Medicine and Science in Sports and Exercise, 43(5). Supplement abstract 2320.

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This study assessed passive and active drag in the four swimming techniques and analyzed the relationship between the coefficient of passive drag and performance. High-level swimmers (M = 4; F = 6) served as Ss. Passive drag was determined by modeling the deceleration curve, obtained by a swim-meter, of underwater gliding. Active drag was assessed through the velocity perturbation method. The assessment of body cross sectional area for the calculation of passive and active drag coefficients was obtained by planimetry and human body volume.

Passive drag was lower than active drag for all swimming techniques. The coefficient of active drag of breaststroke was the highest value in comparison to the other techniques (~0.29, ~0.37, ~0.32, ~0.72) for front crawl, backstroke, butterfly, and breaststroke respectively. There was a high positive correlation (r = 0.81) between the coefficient of passive drag and swimming performance for backstroke. There was no significant relationship between the coefficient of active drag and performance.

Implication. Breaststroke is the least hydrodynamic technique, possibly due to the worst hydrodynamic postures assumed during swimming. Although the coefficient of drag might not be solely the decisive determining factor of swimming performance, it can be considered as a good indicator of swimming technique.

Having a good drag coefficient is a valuable asset in swimming. The single best test for passive drag is the prone push and glide off the wall. Swimmers who glide farthest are "naturally" endowed with a good structure for lower resistance when travelling through water.

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