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

Abstract

A kinematic study allowed to define the three most propulsive positions during 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 positions were different for the ex-world champion Pankratov when compared to another swimmer. Using manikins and a drag-measuring device, we showed that the end of the internal sweep induced the highest drag values and that Pankratov may reduce energy expenditure by taking up a particular position during the end of the swimming cycle. These results point out the relations between swimming movements, passive drag and swimmers' performance.