The moderating role of age in the effect of hip and knee joint functions on explosive power performance in soccer players

Background Explosive power is a key determinant of soccer performance and is closely associated with lower extremity joint function, particularly hip and knee range of motion (ROM) and muscle strength. These factors contribute to essential actions such as jumping, sprinting, and rapid changes of direction; however, their influence may vary across developmental stages due to age-related neuromuscular and physical differences. Despite existing evidence linking strength and flexibility to motor performance, the moderating role of age in these relationships remains unclear in youth soccer players. Therefore, this study aimed to investigate the effects of hip and knee joint ROM and muscle strength on motor performance and to evaluate the moderating role of age in these associations. Methods A total of 59 male soccer players (U15: n = 14, U16: n = 15, U17: n = 15, U19: n = 15) from the youth academies of professional teams participated in the study. ROM values of the hip and knee joints, as well as quadricep and hamstring muscle strength, were measured; subsequently, motor performance assessments were conducted. The data were analyzed using multiple regression models including interaction terms with age, and regions of significance were determined using the Johnson–Neyman technique. Results For the reactive strength index, hip and knee ROM and quadriceps strength were identified as significant predictors; however, these effects were particularly pronounced in soccer players under the age of 17–18 (r 2 = 0.076–0.239; p < 0.01). Similarly, for vertical and horizontal jump performance, hip and knee ROM, as well as quadriceps and hamstring muscle strength, were significant predictors, with these effects again being more evident in players under the age of 17–18 (r 2 = 0.061–0.553; p < 0.01). Conclusion Lower extremity physical characteristics influence motor performance in an age-dependent manner, with stronger effects observed in players under 17–18 years and reduced effects at older ages. These results suggest that training programs for younger age groups may benefit from incorporating range of motion and strength development alongside neuromuscular control exercises, though longitudinal research is needed to confirm causal relationships.