Modelling change and stability of physical and technical performance in young soccer players.

Abstract

This thesis investigates the relationship between changes in young soccer players' physical growth, body shape and composition, biological maturation, physical performance, technical skills, game knowledge and training history within the context of their clubs. A total of 150 players aged 12 to 14 years, at baseline, were selected from participants in the In Search of Excellence in Sport - A Mixed-Longitudinal Study in Young Athletes (INEX) study (2016-2019). INEX was conducted in six soccer clubs of the Porto metropolitan area. They clustered into three age-cohorts (12, 13 and 14 years), were followed consecutively over 4-years using a mixed-longitudinal study design. All data were collected using standardized protocols and the information was distributed over two nested domains: individual - biological, skill/ game proficiency, psychological, and contexts - clubs. Statistical procedures were done in Somatotype calculation, SPSS, LDA, MATLAB, and STATA. Results showed that: (1) older players were more advanced in body physique and their body composition were in line with their advanced biological maturation; (2) older players outperformed their younger peers in all physical performance and technical skills components; (3) these components were related to both advanced maturity and increased training; (4) young soccer players' tactical skills as well as psychological characteristics did not differ across age-cohorts; (5) clubs offer a variety of conditions aiming to enhance players success in their response to training and competition; (6) young soccer players development in speed and agility showed a linear trend, i.e., they improve as time passes; (7) puberty has been found to be a crucial time for nourishing soccer players' future quality vocations in physical performance development; (8) physical performance development is positively associated with biological maturation, higher levels of explosive leg strength, and accumulated hours of soccer specific training; (9) dribbling speed, short-pass rebound and shooting accuracy linearly improved with age, levels of athleticism, and years of official soccer training had positive affect on dribbling speed development; (10) body growth and biological maturation did not independently explain differences in players' trajectories in technical skills; (11) shooting accuracy technique had no significant association with any predictors. We hope that these results may be useful for a more comprehensive approach in young soccer players' long-term preparation in terms of their responses to training and competition.