Split-set resistance training in-season increases maximal vertical power without enhancing athletic performance: a comparison with failure training in youth handball players

BACKGROUND: We tested the hypothesis that splitting resistance training sets would increase lifting velocity and lead to superior athletic performance adaptations, without compromising strength or muscle hypertrophy, compared to volume-matched sets performed to failure in youth handball players. METHODS: Thirty resistance-trained youth handball players (8 females, 22 males; 18±2 years) completed a seven-week lower-body program performed either as all sets to failure (FAILURE) or volume-matched with repetitions split into double the number of sets (SPLIT). Pre- and post-intervention testing included one-repetition maximum (1RM) back squat (BS), squat jump (SJ) force-velocity (FV) profiling, one-legged jump and reach (JR), 20 m and change of direction (COD) sprints, and ultrasound assessment of the quadriceps cross-sectional area (CSA). RESULTS: The mean propulsive training velocity was significantly higher in SPLIT compared to FAILURE (P<0.05). Both groups showed similar improvements in 1RM (15%, both P<0.001) and unloaded SJ height (6%, both P<0.02), with no significant between-group differences in regional or muscle-specific hypertrophy (P>0.05). However, only SPLIT increased maximal vertical power (Pmax, P<0.05) in the FV profile, with a medium effect on theoretical unloaded velocity (V0, ES=0.52, P=0.06). No changes were observed in JR, 20 m sprint, or COD performance in either group (all P>0.1). CONCLUSIONS: These findings indicate that split set resistance training increases training velocity and enhances Pmax but does not translate to superior improvements in strength, hypertrophy, or athletic performance compared to traditional failure training in already trained youth handball players.