AUTHOR=Nobari Hadi , Alves Ana Ruivo , Clemente Filipe Manuel , Pérez-Gómez Jorge , Clark Cain C. T. , Granacher Urs , Zouhal Hassane 

TITLE=Associations Between Variations in Accumulated Workload and Physiological Variables in Young Male Soccer Players Over the Course of a Season

JOURNAL=Frontiers in Physiology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2021.638180

DOI=10.3389/fphys.2021.638180

ISSN=1664-042X

ABSTRACT=<p>This study sought to analyze the relationship between in-season training workload with changes in aerobic power (VO<sub>2m</sub><sub><italic>ax</italic></sub>), maximum and resting heart rate (HR<sub><italic>max</italic></sub> and HR<sub><italic>rest</italic></sub>), linear sprint medium (LSM), and short test (LSS), in soccer players younger than 16 years (under-16 soccer players). We additionally aimed to explain changes in fitness levels during the in-season through regression models, considering accumulated load, baseline levels, and peak height velocity (PHV) as predictors. Twenty-three male sub-elite soccer players aged 15.5 ± 0.2 years (PHV: 13.6 ± 0.4 years; body height: 172.7 ± 4.2 cm; body mass: 61.3 ± 5.6 kg; body fat: 13.7% ± 3.9%; VO<sub>2m</sub><sub><italic>ax</italic></sub>: 48.4 ± 2.6 mL⋅kg<sup>–1</sup>⋅min<sup>–1</sup>), were tested three times across the season (i.e., early-season (EaS), mid-season (MiS), and end-season (EnS) for VO<sub>2m</sub><sub><italic>ax</italic></sub>, HR<sub><italic>max</italic></sub>, LSM, and LSS. Aerobic and speed variables gradually improved over the season and had a strong association with PHV. Moreover, the HR<sub><italic>max</italic></sub> demonstrated improvements from EaS to EnS; however, this was more evident in the intermediate period (from EaS to MiS) and had a strong association with VO<sub>2m</sub><sub><italic>ax</italic></sub>. Regression analysis showed significant predictions for VO<sub>2m</sub><sub><italic>ax</italic></sub> [<italic>F</italic><sub>(</sub><sub>2,</sub><sub>20)</sub> = 8.18, <italic>p</italic> ≤ 0.001] with an <italic>R</italic><sup>2</sup> of 0.45. In conclusion, the meaningful variation of youth players’ fitness levels can be observed across the season, and such changes can be partially explained by the load imposed.</p>