INTRODUCTION: Butterfly swimmers should keep their body as horizontal as possible during the propulsive phases of the arm stroke (Maglischo, 2003). Since 2006, I`ve coached Kawamoto to change his butterfly technique, employing the straight leg kick, which results in a more horizontal stroke. METHODS: This study compared Kawamoto`s performance 2009 and 2005. Each subject performed 25 meter butterfly, from a push start to 15 meter under water butterfly kick. After the 15 meter point, Kawamoto swam all out butterfly stroke until completing a full 25 meters. Swimming Speed Mater (Vine, VMS-003, AC100V, 1/500sec, 0.2mm/pulse) generated the data by an attached wire with movement place. The wire then exports the analogue signals and RS232C signals. These signals calculated are then examined using Microsoft Windows Excel and a Wicoxon Signed Ranked Test. While swimming, the subjects were monitored from the side using an underwater video camera at a sampling frequency of 60Hz (Underwater monitor system 2, YAMAHA, Shizuoka, Japan). The subjects strokes angle of degree was analyzed with DartTrainer in regards to the bending of the knee and upper body movement. RESULTS: Swimming Speed Mater shows the 2009 and 2005 max speed was 2.5m/sec to 2.7m/sec at the second kick phase. The distance pre stroke (DPS) results were different resulting in a, 2.204m±0.131 for 2009 and 1.894m±0.062 for 2005 (DPS (m) Wicoxon.: p=0.006061, 1 stroke (velocity) Wicoxon.: p=0.7748) and DartTrainer showed the upper body movement increased from 61% to 69%. Straight knee considered when the knee bend is 170 degrees to 180degrees (+170 degree), 55% use of straight knee kick for 2009 and 39% for 2005, in the one stroke. DISCUSSION: Based on the above evidence it is clear the most preferre butterfly technique is to use a straight knee kick and to maintain a horizontal body position. Since 2006, we employed the four step training plan in practice and swim meet. First step, we imagined straight kick on the land, second step was to utilize the straight leg fly kick in the pool, third step was to test the technique in a small meet, and fourth step was to utilize the technique in the taper meet.
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