Objective To (i) examine the effect size and the ranking of the training effects for the high-intensity interval training (HIIT), sprint interval training (SIT), and repeated sprint training (RST) on athletes` VO2max through network meta-analysis. (ii) investigate the effects of the training program protocols of the three methods on the improvement of VO2max through pairwise meta-analysis and meta-regression. Methods A systematic search of four databases (Web of Science, PubMed, Scopus, SPORTDiscus) were conducted on April 1, 2025. 51 eligible studies (1,261 athletes), evaluating the direct/indirect effects of HIIT, SIT, RST versus continuous training (CT) and conventional training (CON). Frequentist network meta-analysis quantified effect sizes (NMAs` g) and probabilistic rankings (P-scores), while three-level meta-regression modeled dose-response relationships for training parameters. Results All three interval training methods significantly increased VO2max compared to CON, with NMA rankings: RST (NMA`s g = 1.04) > HIIT (NMA`s g = 1.01) > SIT (NMA`s g = 0.69) > CT (NMA`s g = 0.29), no significant differences existed among RST, HIIT, and SIT (p > 0.05). Subgroup analyses showed HIIT efficacy was moderated by athlete level, whereas SIT improvements were influenced by intervention duration, training frequency, and training mode. Meta-regression identified inverted U-shaped relationships for HIIT, with peak benefits at 140 s work duration and a work-to-recovery ratio (WRR) of 0.85. For SIT, improvements are not significant when recovery durations exceeding 97 s. Conclusions RST, HIIT, and SIT all enhance VO2max in athletes, with RST demonstrating the strongest probabilistic efficacy. Optimal protocols include 3-6 weeks of running-based HIIT (140 s work, 165 s recovery) or SIT (= 30 s sprints, < 97 s recovery) at 3 sessions per week. Conducting RST 3 sessions a week for two weeks is sufficient to achieve improvements. Systematic review registration PROSPERO CRD42023435021.
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