Effects of Run-Specific Isometric Exercises Performed with Complex Training on Neuromuscular Performance in Youth Soccer Players

Abstract

The present study explored whether incorporating run-specific isometric exercises (RSIso) into a complex training (CT) routine would provide additional benefits for youth soccer players during the in-season. Twenty-four male athletes (aged 18–19 years) were randomly divided into two groups: one following a conventional CT program and the other performing an identical program preceded by isometric conditioning training (IST-CT). Both interventions were carried out twice per week for eight weeks, with equivalent training volume and intensity. Performance outcomes were assessed through countermovement jump, drop jump, broad jump (BJ), 30-m linear sprint, and the 5-0-5 change-of-direction (COD) tests. Two-way mixed-design ANOVA (between-subjects factor: group [IST-CT vs. CT]; within-subject factor: time [pre vs. post]) revealed significant main effects of time for COD ability with the non-dominant leg (p = 0.01). Significant group × time interactions were observed for peak power (p = 0.01) and BJ performance (p = 0.03), yet post-hoc comparisons did not confirm statistically meaningful differences (all p > 0.05). Overall, both training approaches led to comparable adaptations in strength-speed performance. Although the direction of changes tended to favor the IST-CT condition, the modest magnitude of effects does not allow to draw definitive conclusions regarding its superiority over conventional CT, indicating that further research is required to confirm the practical relevance of these findings.