Technical factors affecting speed fluctuations and performance in the underwater phase of breaststroke

Mosscrop, Emma Louise (2023) Technical factors affecting speed fluctuations and performance in the underwater phase of breaststroke. Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

Elite swimming races are usually decided by small margins, with the start and turn often being key determinants of race success. This thesis focuses on the underwater phase of the breaststroke start and turn. The first study used data from international competitions to illustrate that GB breaststrokers have room for improvement in their starts and turns, compared to international competitors. This was followed by a series of experimental studies utilising three-dimensional video to analyse the breaststroke underwater phase (BUP) techniques used by elite and sub-elite GB swimmers. Participants differed in when they performed the fly kick within the BUP with the majority adopting the separated technique, where the fly kick was initiated and completed prior to Pull-down. In this group, time spent performing the breaststroke kick was the only temporal metric to correlate strongly with BUP performance (10 m time). Significant differences between elite and sub-elite swimmers were found in durations of Arm recovery and Arm to leg recovery. Correlations were found between BUP performance and mass centre velocity variables in the Fly kick preparation, Pull-down, Glide 2 and Arm + leg recovery phases. Breakout distance, Fly kick preparation phase distance, Arm + leg recovery end of phase distance and Arm + leg recovery minimum velocity distance all correlated strongly with BUP performance. Elite swimmers showed significantly higher mean velocities than sub-elite during the propulsive phases of the Pull-down and Kick, and the Arm + leg recovery. They travelled significantly further underwater during the complete BUP and during the Fly kick prep/recovery, Fly kick upbeat, and Arm + leg recovery phases. Pull-down hand speed correlated strongly with BUP performance for the combined cohort and was higher in the elite than the sub-elite group. The thesis concludes by reporting a five-year technical intervention with a World leading breaststroker. The work demonstrated that through multiple, interdisciplinary interventions, positive changes in performance can be effected: the elite breaststroker reduced his breaststroke start time by 0.26 s.