Vertical Vortices Generated by Flutter Kicks Provide Propulsion and Posture Stability

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A research announcement scientifically elucidating the mechanism by which flutter kicks in crawl swimming contribute to propulsion and posture stability. It demonstrated through actual measurements that vertical vortices created by the left and right feet aid forward movement and suppress body sway.

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A research announcement scientifically elucidating the mechanism by which flutter kicks in crawl swimming contribute to propulsion and posture stability. It demonstrated through actual measurements that vertical vortices created by the left and right feet aid forward movement and suppress body sway.

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Source: https://prtimes.jp/main/html/rd/p/000000375.000119558.html | Date: Date unavailable

This study visualized the water flow generated by flutter kicks in crawl swimming and analyzed how flutter kicks create propulsive force in the water and stabilize posture. The results confirmed that vertical vortices created by the left and right feet not only assist forward movement but also suppress body sway, scientifically demonstrating the role of flutter kicks. To swim fast in water, not only arm movements but also leg movements play a significant role. Much research has been conducted on the "dolphin kick" used in butterfly swimming, and it is known that three-dimensional vortices generated by leg movements lead to propulsion. However, for the "flutter kick" used in crawl swimming, the mechanism by which propulsive force is generated in the water has been poorly understood due to the complex water flow created by alternating leg movements. Therefore, in this study, we investigated and compared the water flow generated by flutter kicks and dolphin kicks in detail using a motion capture system and particle image velocimetry. The results revealed that flutter kicks, similar to dolphin kicks, generate three-dimensional vortices through leg movements, contributing to forward propulsion in the water. On the other hand, unlike dolphin kicks, flutter kicks involve alternating leg movements, causing vertical flows to occur simultaneously around the feet. However, overall, a strong "vertically downward flow" was observed, which was found to lift the body. Furthermore, a significant characteristic of flutter kicks is the formation of asymmetrical vortices, which generate a force that tends to rotate the body sideways, thus playing a role in stabilizing posture during swimming. These research findings are the first to scientifically demonstrate the propulsion mechanism of flutter kicks through actual measurements of water flow, and are expected to lead to improvements in crawl swimming techniques and instruction methods. Research Representatives: Yusaku Nakazono, Projec

Vertical Vortices Generated by Flutter Kicks Provide Propulsion and Posture Stability

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