Hydrodynamic characteristics of competitive swimmers of different genders and performance levels

The purpose of this study was to describe the hydrodynamic characteristics of the four strokes by gender and performance level. Active drag during maximal swimming was measured in each of the four swimming strokes (freestyle, butterfly, backstroke, and breaststroke) on males and females of varying ability levels using the perturbation method developed by Kolmogorov and Duplisheva(1992). Active drag (F-Da), the hydrodynamic coefficient (Cx(Da)), and total external mechanical power output (Pto) were calculated at each swimmer's maximal swimming velocity. There were complex, non-linear relationships between maximum swimming velocity and the three hydrodynamic indicators. The four swimming strokes were ranked in order of resistance based on the three hydrodynamic indicators. The order, from least to most resistance, was (1) freestyle, (2) backstroke, butterfly, (3) breaststroke. No statistical difference was seen between the backstroke and butterfly. Within each stroke, the most important factor for reducing active drag appeared to be individual biomechanical technique.