The impact of long-term soccer-specific training on the physical development of elite junior soccer players

The goal of any soccer talent development programme is to guide players towards professional characteristics. In order to maximise this process it is essential to gain an insight into their individual characteristics. Within this specific population there are many factors from maturation, hormonal, anatomical and musculoskeletal changes that accompany paediatric development and consequently have a direct impact upon their development. The aim of this thesis was to determine the relative influence of changes in maturation and long-term systematic training on the physical development of elite junior soccer players. The aim of the first study (Chapter 4) was to assess the reliability of a range of anthropometric and performance measures in aged matched academy and non-academy soccer players (U14-18). The results demonstrated that all anthropometric (%CV values of 0.1 – 1.3%) and performance measures (%CV values of 1.8-6.2%) were highly reproducible in both the academy and non-academy soccer players. These assessments would be subsequently used to determine the impact of long-term training on changes in physical development of junior soccer players. The aim of study two (Chapter 5) was to determine the validity of a non-invasive approach (maturity offset) for predicting end height stature in academy soccer players (U14-18). Overall, agreement between estimates of end height stature in elite youth soccer players’ using skeletal x-ray and the maturity-offset method were poor with a SEM and 95 % LOA of 4 cm and +11cm being observed respectively. These findings indicate that care must be taken when predicating end height stature in academy soccer players when using maturity offset method. The aim of the third study (Chapter 6) was to examine the typical weekly training load experienced by academy and non-academy soccer players (U12-U16) during the in-season competitive period. Physiological loading associated with training sessions and match-play were monitored using heart rate (HR) and ratings of perceived exertion (RPE). Training and match loads were calculated by multiplying global session RPE and duration (RPE-TL). Weekly training load in the academy players (U12, 737±51; U14, 646±106; U16, 750±81) was higher than the non-academy players (U12, 157±28; U14, 161±19; U16, 193±26) across the three age groups. Similarly, match load and % time spent >90%HRmax was higher in the academy players compared to the non-academy players. The present findings indicate that the overall load and intensity of training is greater in academy players compared to aged match non-academy players. The aim of the fourth study (Chapter 7) was to determine the relative influence of changes in maturation and long-term systematic training on changes in physical performance in age matched academy and non-academy junior soccer player. The three-year change in the physical performance of twenty-seven academy and eighteen non-academy soccer players (U12-U16) were monitored. When corrected for differences in both baseline performance and change in maturity status (maturity offset), greater changes in countermovement jump (7.3 + 2.6 cm, 5.4 + 2.5 cm), 10 m (-0.15 + 0.05 s, -0.10 + 0.04 s) and 20 m sprint (-0.30 + 0.16 s, -0.15 + 0.13 s), agility (-0.19 + 0.01 s, -0.08 + 0.08 s), repeated sprint (-0.60 + 0.26 s, -0.41 + 2.1 s) and intermittent endurance capacity (1128 + 406 m, 315 + 370 m) were observed in the Academy players compared with non-academy players (p 0.7). These findings indicate that long-term player development programs accelerate the rate physical development of academy soccer players relative to age and maturity matched non-academy players. In summary, the present thesis highlights that academy soccer players experience greater rates of improvement in physical performance indicators compared to non-academy players, independently from the initial performance level of the child and change in maturation over the same time period. These difference are likely to reflect the increased volume and intensity of soccer-specific training experienced by the young soccer players as part of the academy’s approach to long-term athlete development. Future research is warranted in order to determine training loads in elite youth soccer players at different stages of biological maturity which serve to enhance performance whilst minimising the risk of injury.