Long-term changes in the speed curve of a world-class butterfly swimmer.

Background This study described the changes in selected points of the speed curve, stroke rate (SR), and stroke length (SL) of an elite butterfly swimmer and examined their relationship with average speed (AS) and competitive performance. Methods Over eight years, the male swimmer (50 and 100 m: 22.70 and 51.47 s) underwent 18 tests to assess AS, SR, SL, intracyclic speed variation (ISV), and eight selected points of the speed curve. Peak1 is the maximum speed in the upward kick executed during the arm recovery. Peak2 is the maximum speed in the first downward kick after the arm entry into the water. Peak3 is the maximum speed during the arm pull. Peak4 is the maximum speed during the arm push combined with the second downward kick. Min1, Min2, Min3, Min4 corresponds to the minimum speeds found respectively before each peak speed. Official competitive results in 50 (50BF) and 100 m (100BF) within three weeks of the speed tests were registered. Results SR (r = .736), ISV (r = -.493), Peak1 (r = .555), Min2 (r = .558), and Min3 (r = .539) correlated with AS. 50BF correlated with AS (r = -.658) and Peak1 (r = -.820), whereas 100BF with AS (r = -.676), SR (r = -.571), Peak1 (r = -.758), and Peak2 (r = -.594). Conclusions AS increased by improving SR, Peak1 and Peak3. Increases in Min2 and Min3 indicate better transitions from resistive to propulsive phases. Selected points of the speed curve may predict butterfly performance.