Identification of Key Performance Variables in Prone and Supine Underwater Dolphin Kick

Jones, Victoria M. (2023) Identification of Key Performance Variables in Prone and Supine Underwater Dolphin Kick. Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

In freestyle, backstroke, and butterfly races, swimmers may travel up to 15 m underwater following the dive entry and after the wall push-off in turns. The underwater dolphin kick (UDK), a cyclical movement comprising oscillations of the segments of the lower limb, is customarily used in this underwater phase. It was unknown whether kinematics and coordination patterns differed between UDK performed prone and supine. This thesis contributes to the current body of knowledge on the key performance variables of prone and supine UDK technique, thereby providing practical outcomes for coaches and practitioners to assess and improve UDK. Four studies were conducted to determine: 1) how start and turn performance of Great Britain’s (GB) swimmers compare with the rest of the world, 2) if a velocity-meter can be used interchangeably with video-based measurement of UDK speed, 3) if key kinematic metrics differ between prone and supine UDK, and 4) if coordination patterns differ between prone and supine UDK. Relative to clean swimming speeds, GB had slower starts and turns than the rest of the world in some events, but were equal to or faster in other events. Compared to the video-based method, the velocity-meter over- and under-estimated maximum and minimum kick cycle speeds, respectively; mean speeds were similar. With the exception of one upper body metric, no significant differences were found between prone and supine UDK kinematics. Differences were found between sexes, with males demonstrating significantly larger kick amplitude, maximum toe speeds, and distance per kick. Males reached maximum knee separation earlier in the kick cycle, and minimum foot separation later than females. Hip extension velocity, knee flexion velocity, and ankle plantar-flexion velocity were key determinants of UDK performance. Faster kickers maintained horizontal centre of mass speed over the entire underwater phase better than the slower kickers. A temporally sequential movement pattern was found for the knee flexion phase, but not the knee extension phase. Furthermore, coordination patterns between the hip and knee, and knee and ankle, did not differ significantly between prone and supine kicking. This thesis demonstrated that, though individual differences in technique do exist, the kinematics and coordination patterns observed in prone and supine UDK do not differ significantly.