Effects of Drafting on Hydrodynamic and Metabolic Responses in Front Crawl Swimming

JANSSEN, M., B. D. WILSON, and H. m. TOUSSAINT. Effects of Drafting on Hydrodynamic and Metabolic Responses in Front Crawl Swimming. Med. Sci. Sports Exerc., Vol. 41, No. 4, pp. 837-843, 2009. Purpose: Effects of drafting on the hydrodynamic and metabolic responses of the drafter behind and at the side of a passive and an active lead swimmer were related to the influence of a lead swimmer oil the flow field of the draftee. Methods: Passive drag of the draft swimmer was compared for the nondrafting condition. in the drafting conditions behind a passive and an active lead swimmer, and at the side of a passive and an active lead swimmer. The effect was also evaluated with oxygen uptake measurements. Fluid pressure measurements were made behind and at the side of a passive and all active lead swimmer to examine the flow field. Results: Behind a passive lead swimmer, passive drag was significantly reduced by 20%, and behind an active lead swimmer, it was reduced by 9%. At the side of a passive lead swimmer, passive drag was significantly increased by 9%, and at the side of all active lead swimmer, it increased by 8%. Oxygen uptake was significantly reduced by 25% behind a passive lead swimmer, by 11% behind all active lead swimmer, and only marginally changed at the side of a lead swimmer. The pressure measurements indicated a 33% decrease in mean flow velocity behind an active lead swimmer but all increase in peak flow velocities due to the kick of the lead swimmer. These increases could explain the lesser decrease in passive drag behind all active versus a passive lead swimmer. Conclusion: The best position for a draft swimmer was found to be directly behind all active lead swimmer at a distance of 0.50 m between the toes of lead swimmer and the hands of drafter, with significant reductions in both passive drag and oxygen uptake when drafting.