Characteristics Of Butterfly Stroking Skill In Elite Swimmers Detected By Means Of A Speed Meter

Abstract

A speed meter that measures a subject's moving velocity by pulling a fine wire over a generator (Maglischo, 2003) for a distance of 25m was developed for use with competitive swimmers. In our previous study, the authors used the speed meter to check for skill differences between competitive breaststroke swimmers of international achievement and collegiate breaststroke swimmers who had not reached national or international levels. The results showed that this method was useful for identifying differences in skill between the two groups of swimmers. PURPOSE: In this study the authors applied the speed meter to the butterfly stroke in order to study the skills of elite swimmer. METHODS: Subjects were four male competitive butterfly stroke swimmers, i.e., one who had reached international level (ranked 3rd in the world in 2006), and three who had reached the national but not international level. The velocity curves were compared among these swimmers. The wire line of the speed meter was attached to swimmers by means of a belt and their intracyclic velocity changes were recorded precisely for several stroke cycles while swimming at maximum speed. The average velocity changes for one stroke cycle were calculated with data from all successive stroke curves. The average stroke cycles were compared among the four subjects. RESULTS: Four propulsive phases were picked up from each average stroke cycle. They were as follows; 1) first kick phase, 2) insweep phase, 3) upsweep and second kick phase, and 4) wave phase (during the arm recovery). Average velocities during each phase were compared among the four swimmers. In consequence, no significant differences were observed between three national level swimmers for all phases. Additionally, there were no significant differences among four swimmers for first kick phase, insweep phase, and wave phase. However, for upsweep and second kick phase, a significantly higher average velocity was observed for the international level swimmer compared with the other swimmers (Steel-Dwass Test, p<0.05). CONCLUSIONS: It was suggested that improvements in butterfly stroke for elite swimmers were dependent upon improving average velocity during the upsweep and second kick phase.