In Japan, the analysis of swimming race performance in major national competitions have been conducted for more than 30 years by Japan Swimming Federation scientific committee. The results of the race analysis showed that not only the performance of free-swimming component, but also the start, turn and finish components performances affected the outcome of the competition. Generally, swimmers move underwater after the turn, so the performance of turn-out could be affected by the underwater-distance covered by the swimmer after the push-off from the turning wall. However, underwater phase after the turn had never been analyzed in major Japanese competitions. Therefore, this study aimed to analyze the underwater phase after the turn and its relation to race performance in Japanese elite male 200 m swimmers. In total, the performances of 190 male 200 m swimmers were analyzed. We recorded all the races with two video cameras which were synchronized with the official timing system. For each turn in 200 m event, turn-out time was calculated from the time when the swimmer`s head reaches 65, 115 and 165m marks, and the official 50, 100 and 150 m split times, respectively. Also, the underwater-distance covered by the swimmer after pushing off the turning wall were analyzed using 2D-DLT technique. The average underwater-distance for the turns in 200 m event differed among each stroke: backstroke, 9.65 ± 1.96 m; breaststroke, 9.22 ± 0.85 m; butterfly, 8.28 ± 1.50 m; freestyle, 6.32 ± 1.25 m. Positive correlations were found between the official result and the turn-out time, and negative correlation were found between the underwater-distance and the turn-out time for all strokes, which indicated that faster swimmer had shorter turn-out time and covered longer underwater-distance after pushing off the turning wall.
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