Comparison of Functional and Traditional Strength and Power Training on U19 Soccer Players During Offseason in Norway: A Randomized Controlled Trial.

Engberg Treu Lassen, L, Kersting, UG, and Pessoto Hirata, R. Comparison of functional and traditional strength and power training on U19 soccer players during off-season in Norway: A randomized controlled trial. J Strength Cond Res XX(X): 000-000, 2026-Functional training emphasizes multiplanar, soccer-specific movement patterns requiring body control, whereas traditional resistance training focuses on maximal force production through stable, bilateral lifts. Although both approaches are common in soccer physical preparation, their relative effects on soccer-specific performance remain uncertain. This study compared the effects of functional vs. traditional strength training on performance outcomes during the offseason in U19 male players. Thirty-three Norwegian players were randomly allocated to a functional training group (FTG, n = 11), a traditional training group (TTG, n = 11), or a control group (CG, n = 11) using stratified, concealed allocation. During the first 4 weeks, all groups completed 2 weekly soccer sessions; FTG and TTG additionally completed 2 supervised 70-minute strength sessions per week. In the final 4 weeks, FTG and TTG continued the twice-weekly strength training, whereas CG ceased organized training. Functional training group performed unilateral, multiplanar free-weight exercises, while TTG performed bilateral, uniplanar machine-based exercises. The primary outcome was technical soccer performance, with mobility, dynamic balance, sprint speed, change of direction, and vertical jump as secondary outcomes. Both FTG and TTG improved Loughborough Soccer Shooting Test (LSST) performance compared with CG (FTG: -0.43 seconds, p = 0.003, d = 1.62; TTG: -0.50 seconds, p < 0.001, d = 1.88). Traditional training group also increased body mass compared with the CG (2.20 kg, p = 0.002, d = 1.65). Functional and traditional strength training produced comparable improvements in LSST time. These findings highlight training dose response and support individualized off-season programs integrating physical preparation with sport-specific demands.