The effect of a differentiated training process on the dynamics of physical and technical fitness of young football players aged 14–15

Abstract

Topicality. In youth football, the same chronological age does not reflect individual differences in the rate of biological development, which may result in substantial differences in physical and technical fitness. This is particularly relevant for retarders, who, due to slower biological development, may have lower baseline performance than accelerators and normotypical peers. Therefore, the use of a uniform approach to planning training stimuli limits the possibility of individualized training. Despite the considerable body of research examining the relationship between biological maturity and fitness indicators in young football players, the targeted differentiation of the training process according to the rate of biological development, particularly for athletes with slower development, remains insufficiently studied. This highlights the relevance of investigating changes in the physical and technical fitness of football players aged 14–15 according to the rate of biological development and assessing changes in retarders under differentiated training conditions. The purpose of the study. To determine the dynamics of physical and technical fitness in football players aged 14–15 years with consideration of the rate of biological development. Research material and methods. The study included 21 football players: 9 normotypical athletes, 5 accelerators, and 7 retarders. The rate of biological development was determined based on the ratio of the actual to normative values of the latent period of sensorimotor reaction. Physical and technical fitness was assessed using a battery of standardized field tests. In 2025, retarders received additional differentiated training stimuli lasting 15–25 min. The paired Student’s t-test and Wilcoxon signed-rank test were used to assess within-group changes; one-way analysis of variance (ANOVA) and the Kruskal–Wallis test were used for between-group comparisons; and Hedges’ g was calculated to estimate effect size. Research results. Accelerators demonstrated the highest performance, whereas retarders showed the lowest. Normotypical athletes demonstrated positive changes in five indicators, whereas no statistically significant changes were identified in accelerators. Retarders demonstrated statistically significant positive changes in nine of the eleven indicators. The largest effects in retarders were observed for the Ruffier index (g = −1.49) and standing long jump (g = 1.12). No statistically significant between-group differences in the magnitude of changes were identified (p > 0.05). Conclusions. The rate of biological development may serve as an additional criterion for individualizing the training of young football players. In retarders, differentiated training was accompanied by positive changes in the majority of assessed indicators. However, a causal effect of the program was not established. Further studies involving larger samples and longer observation periods are warranted.