ACTIVE DRAG CHANGES BETWEEN TRAINING SEASONS IN YOUNG SWIMMERS

Abstract

The purpose of this study was to verify the changes in the hydrodynamic profile of young swimmers from one training year to the next. Twelve male and eight female swimmers (initial age: 13.87 ± 0.82 and 12.45 ± 0.34 years) were evaluated in front crawl using the velocity perturbation method, for determination of maximal velocity (Vmax), active drag (D.), drag coefficient (CD.) and power output. Interval between 1st and 2nd evaluations was 9 months. Female swimmers showed lower CD. at the 2nd: evaluation, probably caused by stronger technical improvement. In spite of dramatic increases in body mass, competitive performance, and Vmax , D. and CD. remained unchanged and the Froud number for a fixed velocity of .5 m.s· 1 decreased, in both genders. Reduced Froud number, dependent on body height, may have counterbalanced the effect of increased Vmax and body mass, reducing the wave drag component.