Active and passive drag: the role of trunk incline
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The aim of this study was to investigate the role of trunk incline (TI) and projected frontal area (Aeff) in determining drag during active/passive measurements. Active drag (Da) was measured in competitive swimmers at speeds from 0.6 to 1.4 m s−1; speed specific drag (Da/v2) was found to decrease as a function of v (P < 0.001) to indicate that the human body becomes more streamlined with increasing speed. Indeed, both Aeff and TI were found to decrease with v (P < 0.001) whereas Cd (the drag coefficient) was found to be unaffected by v. These data suggest that speed specific drag depend essentially on Aeff. Additional data indicate that Aeff is larger during front crawl swimming than during passive towing (0.4 vs. 0.24 m2). This suggest that Da/v2 is larger than Dp/v2 and, at a given speed, that Da is larger than Dp.