Application of the Performance Index for Monitoring Anaerobic Endurance of Competitive Swimmers

The purpose of the study was to investigate the effectiveness of the performance index (PI) in monitoring anaerobic endurance of adult competitive swimmers during a nine-week intervention. The study included 30 male competitive swimmers. Participants were allocated to an advanced or an intermediate group, taking into account their training experience and sport results. Each participant was tasked with swimming eight lengths of a 25-m pool at maximum speed and full commitment with front crawl and with 15-s rest intervals between subsequent laps at the start of the intervention (pre-test) and nine weeks later (post-test). The performance index determined by the average speeds in successive laps was analysed. No statistically significant differences were observed between the groups in the calculated performance index at the end of the training cycle. A repeated measures ANOVA revealed an interaction between TIME (a repeated factor) and GROUP (a fix factor) (F1.28 = 25.45, p < 0.0001, η² = 0.476). Swimmers from the intermediate group significantly improved their PI (p = 0.0002), while the advanced swimmers did not. Coaches could apply the methodology presented in this study to the specific requirements of their disciplines. The adaptability of the performance index method makes it a valuable tool for assessing anaerobic endurance among athletes of varying experience levels, though it does not serve as a means to directly enhance anaerobic endurance.