Hydrodynamics optimization in butterfly swimming: position, drag coefficient and performance

A kinematic study allowed to define the three most propulsive positions dur ing a butterfly swimming cycle, which were: the end of the external sweep, the end of the internal sweep and the end of thrust. These instantaneous po sitions were different for the ex-world champion Pankratov when compared to another swimmer. Using manikins and a drag-measuring device, we showed tha t the end of the internal sweep induced the highest drag values and that Pa nkratov may reduce energy expenditure by taking up a particular position du ring the end of the swimming cycle. These results point out the relations b etween swimming movements, passive drag and swimmers' performance. (C) 1999 Elsevier Science Ltd. All rights reserved.