Visualizing how flutter kick vertical vortices generate propulsion and suppress body sway in swimmers

Researchers at University of Tsukuba used advanced techniques to visualize the water flow generated by flutter kicking during front-crawl swimming. They analyzed how this kicking motion generates propulsive force and contributes to body stabilization, demonstrating that the vertical vortices resulting from the alternating left and right leg movements not only impart forward propulsion but also suppress body sway. These results provide a fluid-dynamical explanation of the functional value of the flutter kick.