A Simplified Method for Determination of Critical Swimming Velocity as a Swimming Fatigue Threshold for Sprinters and Distance Swimmers

Abstract

Critical swimming velocity (Vcri) is recognized to be the swimming speed corresponding to the maximal lactate steady state, and is expressed as the slope of a regression line between swimming distances and their sustained times. In order to determine Vcri, the conventional practical test requires a swimmer to swim a distance of 200 m and 400 m twice. The purpose of this study was to find a simpler method for the determination of Vcri. Eight sprinters (50 m and 100 m freestyle) and eight distance swimmers (400 m and 1,500 m freestyle) performed 50 m, 100 m, 200 m, 300 m, 400 m and 1,500 m at maximal effort in a 25 m-swimming pool. The obtained Vcri were 1.409 ± 0.064 m/sec for sprinters and 1.482 ± 0.026 m/sec for distance swimmers. Then, so as to find the simpler method, the relationships between Vcri and swimming velocities at each swimming distance (V 50 m, V 100 m, V 200 m, V 300 m, V 400 m and V 1,500 m) were investigated. As a result, both sprinters and distance swimmers showed significant relationships between Vcri and swimming velocities at distances over 200 m. From the viewpoint of the aerobic energy supply system to muscle, however, V 300 m was the most appropriate swimming velocity to estimate Vcri as an endurance index from the shortest swimming distance. In order to make sure that Vcri shows the maximal lactate steady state, the subjects were instructed to swim 2,500 m at the three constant velocities (98.5%, 100%, and 101.5% of Vcri). As a result, 100% of Vcri showed a higher steady state than 98.5% of Vcri, but 101.5% of Vcri did not show the steady state. Thus, we recognized that 100% of Vcri was at the highest steady state level. In conclusion, one timed 300 m maximal effort swimming test is believed to be a simpler, more rational method to determine Vcri for both sprinters and distance swimmers.