Underwater flutter kicking causes deceleration in start and turn segments of front crawl.

This study investigated the deceleration effect of flutter kicking after dolphin kicking before commencing the stroke at swimmer's emersion. Eight male competitive swimmers (age 19.6 ± 1.2 years; Fédération Internationale de Natation points 733.6 ± 57.5) performed 15 m front crawl sprints from wall push-off three times in a row, with two types of underwater kicks [dolphin kick only (dolphin condition) and dolphin kick followed by flutter kick (dolphin-flutter condition)]. Sprint bouts were divided into four phases. Phases 1 and 2 were defined, respectively, as the fourth and fifth dolphin kicks. Phase 3 was defined as the first stroke (dolphin condition) and six beats of the flutter kicking (dolphin-flutter condition). Phase 4 was defined as the second stroke (dolphin condition) and the first stroke (dolphin-flutter condition). Two-way repeated measured analysis of variance on mean swimming velocities demonstrated an interaction of condition and phase (p < 0.001) and a simple main effect (p < 0.001) at Phase 3. These results indicated greater deceleration due to adding the flutter kick after the dolphin kick before commencing the stroke. Swimmers should use only the underwater dolphin kick before commencing the front crawl in start and turn segments.