Background: This systematic review and meta-analysis evaluated the effects of HIIT-based interventions on cardiorespiratory fitness, jump, sprint, change-of-direction, and repeated sprint ability in trained adolescent athletes, and explored potential moderators of these effects. Methods: PubMed, Scopus, Embase, Web of Science, and the Cochrane Library were systematically searched. Between-group effect sizes were calculated from pre-to-post changes and pooled using random-effects models. Risk of bias and certainty of evidence were assessed using the Cochrane RoB 2 tool and the GRADE approach. Heterogeneity was assessed using I², and prespecified subgroup, sensitivity, and meta-regression analyses were performed when appropriate. Results: Thirty-five studies involving 988 trained adolescent athletes were included. Compared with non-HIIT control conditions, HIIT-based interventions significantly improved VO2max (SMD = 0.65, 95% CI 0.46 to 0.83, I² = 0%), field-based intermittent endurance test performance, including Yo-Yo IR1, Yo-Yo IR2, and the 20m multistage fitness test (SMD = 0.65, 95% CI 0.07 to 1.23, I² = 79.4%), final velocity reached in the 30-15 Intermittent Fitness Test (VIFT) (SMD = 1.13, 95% CI 0.63 to 1.63, I² = 42.5%), countermovement jump (CMJ) (SMD = 0.44, 95% CI 0.13 to 0.74, I² = 62.7%), =10m sprint performance (SMD = -0.79, 95% CI -1.26 to -0.32, I² = 50.1%), =20m sprint performance (SMD = -0.28, 95% CI -0.47 to -0.08, I² = 0%), and change-of-direction (COD) (SMD = -0.54, 95% CI -0.72 to -0.37, I² = 0%). For repeated sprint ability (RSA), all included interventions were repeated sprint training (RST), and the pooled effect was significant (SMD = -0.70, 95% CI -1.02 to -0.39, I² = 12.7%). Significant between-subgroup differences were found only for age in field-based intermittent endurance test performance (p = 0.033) and competitive level in =20m sprint performance (p = 0.034), although these subgroup findings should be interpreted as exploratory. Conclusion: HIIT-based interventions may improve multiple physical fitness outcomes in trained adolescent athletes, with larger effects observed for VO2max, field-based intermittent endurance test performance, VIFT, and =10m sprint. Improvements in CMJ, =20m sprint, and COD were smaller. For RSA, current evidence mainly supports a beneficial effect of RST. Systematic review registration: https://www.crd.york.ac.uk/PROSPERO/, identifier CRD420261348570.
© Copyright 2026 Frontiers in Physiology. Frontiers Media. Alle Rechte vorbehalten.