Effects of the Football+ warm-up program on eccentric hamstring strength and dynamic balance in youth male players: A cluster-controlled trial

This cluster-allocated interventional study examined the effects of the Football+ warm-up program on isokinetic muscle strength and dynamic balance in youth amateur male football players. Two Iranian U18 teams voluntarily participated, completed introductory sessions, and were team-allocated to either the Football+ (n = 15, age = 17.31 ± 0.12 years) or a control group (n = 16, age = 17.13 ± 0.09 years). Baseline assessments included concentric and eccentric quadriceps and hamstring strength at 60°/s and 180°/s, and dynamic balance using the Biodex Balance System. The intervention group performed the Football+ twice weekly for eight weeks, while the control group continued its regular warm-up routines. All assessments were repeated post-intervention. Repeated-measures ANOVA and non-parametric equivalents were used to analyze group differences at a significance level of p ≤ 0.05. ANOVA revealed significant time × group interactions for hamstring eccentric strength at both 60°/s and 180°/s in both legs, whereas quadriceps strength did not change significantly. For dynamic balance, a significant time-group interaction was observed for anterior-posterior stability of the right leg (p = 0.03). For the left leg, a Kruskal-Wallis test indicated a significant pre-intervention difference favoring the control group (p = 0.028), which was no longer present post-intervention (p = 0.42). Overall stability improved significantly over time in the Football + group without significant interaction effects. Eight weeks of the Football+ training (level 1) was associated with improvements in hamstring eccentric strength and selected aspects of dynamic balance, suggesting potential benefits for neuromuscular performance in youth amateur players. Further studies with larger samples across different age groups and playing levels are warranted.