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Hum Mov Sci. 2013 Dec;32(6):1214-25. doi: 10.1016/j.humov.2012.07.009. Epub 2013 Sep 24.

Characterization of speed fluctuation and drag force in young swimmers: a gender comparison.

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National Institute of Education, Nanyang Technological University, Singapore; Research Centre in Sports, Health and Human Development, Vila Real, Portugal. Electronic address:


The aim of this study was to compare the speed fluctuation and the drag force in young swimmers between genders. Twenty-three young pubertal swimmers (12 boys and 11 girls) volunteered as subjects. Speed fluctuation was measured using a kinematical mechanical method (i.e., speedo-meter) during a maximal 25-m front crawl bout. Active drag, active drag coefficient and power needed to overcome drag were measured with the velocity perturbation method for another two maximal 25m front crawl bouts with and without the perturbation device. Passive drag and the passive drag coefficient were estimated using the gliding decay velocity method after a maximal push-off from the wall while being fully immersed. The technique drag index was also assessed as a ratio between active and passive drag. Boys presented meaningfully higher speed fluctuation, active drag, power needed to overcome drag and technique drag index than the girls. There were no significant gender differences for active drag coefficient, passive drag and passive drag coefficient. There were positive and moderate-strong associations between active drag and speed fluctuation when controlling the effects of swim velocity. So, increasing speed fluctuation leads to higher drag force values and those are even higher for boys than for girls.


3720; Active drag; Children; Front crawl; Hydrodynamics; Kinematics; Passive drag

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