Background: We focused out analysis on the straightness of the knee for the butterfly kick. The effectiveness of using a straight knee kick for the world class swimmers during 100
meter butterfly competitions kick. We compare the performance of the Asian record holder in 2005 (53.86 in 100Fly) to 2009 (51.00 in 100Fly) angle of butterfly kick, and find the straightness of the
butterfly kick significantly improves the performance. Beginning in 2006, we coached the subject to change his butterfly technique, employing a straightness butterfly kick, which resulted in a more
horizontal stroke. The subject’s initial butterfly kick technique previously employed a bent knee butterfly kick technique, but was changed to a more straight knee technique. The technique of
straightness knee butterfly kick slows kick speed, makes more lactate. The straightness knee butterfly kick makes to increase one stroke velocity, Distance per stroke and max speed.
Methods: The subject, the men’s 100 meter butterfly FINA (Federation Internationale de Natation Amateur) world ranking 9th in the history, and FINA world record (FINA, 2014) . The
subject kick speed analyzed with Kinovea (0.8.15, 1GHz, 256Mo) in regards to the butterfly kick speed by 1/500sec, and underwater high speed HD camera (Panasonic HDMI:1080i 720p 480pHX-WA30). The
lactate test was 50seconds wall kick; tempo was 1.10sec/stroke by FINIS tempo machine. The subject lactate generated by the Lactate ProTM LT-1710 (Arkray, 5μl, Kyoto, Japan) meter for on-farm
determination of the blood lactate of teleost fishes (Vescovi, 2010). A Swimming Speed Meter (Vine, VMS-003, AC100V, 1/500sec, 0.2mm/pulse) using a wire attached to the swimmer, exported the analogue
signals via an RS232C post to a computer. These signals were used to calculate swimming speed with Microsoft Windows Excel and a Wilcoxon Signed Ranked Test.
Results: The DartTrainer and Kinovea measures the kick speed and reported the straight knee butterfly kick speed was an average of 1.18m·s-1, while the bending knee butterfly kick
average speed was 1.61m·s-1. The lactate Acid test revealed that the bent knees test result at 4.3mmol/l compared to the straight knee test at 6.7mmol/l. Swimming Speed Mater shows the 2009 and 2005
max speed was 2.5m/sec to 2.7m/sec at the second kick phase respectively. 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)
Wilcoxon.: p=0.006061, 1 stroke (velocity) Wilcoxon.: p=0.7748).
Conclusions: This paper reveals the relationship between efficiency and effectiveness of the straight knee butterfly kick. Although straight knee technique results in high speeds and
better body position, it also creates more lactic acid. Swimmers using this technique should be aware of the potential benefits of using a straight knee kick, but also the potential shortcomings. The
results of this paper reveal that with proper training and technique, the straight knee butterfly kick can result in much faster 100 meter butterfly times for swimmer able to mitigate the increase in
lactic acid production during competition.