Performance trial (eggbeater kick ability)
Participants conducted the performance trial measurements in a 50-m indoor pool with a maximum depth of 3.8 m. A blood sample was taken from the fingertip and blood lactate levels were measured with Lactate Pro2 (Arkray. Kyoto. Japan) before and after the performance trial. Participants performed a 20-second eggbeater kick while holding a 10-kg weight (with no arm sculls) and keeping their manubrium (superior part of the sternum) above the water surface. Afterward, the participants stood on the underwater sidewalk (staging point on the pool wall) and rested for 20 seconds with the weight on the poolside. This interval exercise (20-second eggbeater kick + 20-second rest) was performed as one set until exhaustion. During the test, subjects were instructed to maintain as high a body position as possible; when participants could no longer maintain the reference line (upper sternal border at the water surface), they were considered exhausted, and the test was stopped.