, Volume 106, Issue 2, pp 195-205
Date: 18 Feb 2009

Active and passive drag: the role of trunk incline

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Abstract

The aim of this study was to investigate the role of trunk incline (TI) and projected frontal area (A eff) in determining drag during active/passive measurements. Active drag (D a) was measured in competitive swimmers at speeds from 0.6 to 1.4 m s−1; speed specific drag (D a/v 2 ) 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 A eff and TI were found to decrease with v (P < 0.001) whereas C d (the drag coefficient) was found to be unaffected by v. These data suggest that speed specific drag depend essentially on A eff. Additional data indicate that A eff is larger during front crawl swimming than during passive towing (0.4 vs. 0.24 m2). This suggest that D a/v 2 is larger than D p/v 2 and, at a given speed, that D a is larger than D p.