Handball small-sided games and running-based high-intensity interval training similarly improve sprint, change-of-direction, and repeated-sprint performance in untrained young adults.

To compare small-sided handball games (SSG) and high-intensity interval training (HIIT) on speed, change of direction (COD), and repeated sprint ability (RSA) in untrained adults. Randomized controlled trial with blinded outcome assessors. Ninety untrained participants (19.82 ± 0.66 years; 45 women) were randomized 1:1:1 to handball SSG, HIIT, or control (n = 30 each). SSG and HIIT trained 3 sessions/week for 16 weeks; control received no structured training. Outcomes were 10-m sprint time, 5-0-5 COD time, and RAST-derived RSA peak power (PP) and fatigue index (FI). Intention-to-treat linear mixed models estimated group×time effects. Compared with control, both handball SSG and HIIT reduced 10-m sprint time (SSG MD − 0.300 s, 95%CI − 0.443 to − 0.158; HIIT − 0.303 s, − 0.446 to − 0.161; p < 0.05) and improved COD (SSG − 0.415 s, − 0.555 to − 0.276; HIIT − 0.287 s, − 0.427 to − 0.148; p < 0.05). RSA-PP increased (SSG 66.793 W, 1.356 to 132.231; HIIT 82.443 W, 17.006 to 147.881; p < 0.05) and RSA-FI decreased (SSG − 5.180%, − 8.052 to − 2.308; HIIT − 5.747%, − 8.618 to − 2.875; p < 0.05). SSG and HIIT did not differ for any outcome (all p > 0.05). In this sample, 16 weeks of handball SSG or HIIT improved sprint, COD, and RSA versus no training. Any modality-specific advantage appears small and should be interpreted cautiously.