Abstract
This study sought to analyze the relationship between in-season training workload with changes in aerobic power (VO2max), maximum and resting heart rate (HRmax and HRrest), 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%; VO2max: 48.4 ± 2.6 mL⋅kg–1⋅min–1), were tested three times across the season (i.e., early-season (EaS), mid-season (MiS), and end-season (EnS) for VO2max, HRmax, LSM, and LSS. Aerobic and speed variables gradually improved over the season and had a strong association with PHV. Moreover, the HRmax 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 VO2max. Regression analysis showed significant predictions for VO2max [F(2, 20) = 8.18, p ≤ 0.001] with an R2 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.
Highlights
Soccer, an intermittent-activity profile sport, integrates explosive activities that require high power output of the lower limb muscles, being interspersed by low-intensity activities with brief recovery intervals (Mohr et al, 2005; Bradley et al, 2014)
The study sample consisted of 23 young male sub-elite soccer players who compete at a national U16 level
There were significant correlations between VO2max at EaS to MiS (r = 0.49; 95% CI, 0.09–0.76; p = 0.02), linear sprint short test (LSS) at EaS to MiS (r = −0.46; 95% CI, −0.74 to −0.05; p = 0.02), and LSS at MiS to EnS (r = 0.51; 95% CI, 0.11–0.76; p ≤ 0.001) with peak height velocity (PHV)
Summary
An intermittent-activity profile sport, integrates explosive activities that require high power output of the lower limb muscles (e.g., sprints, changes of direction, jumps), being interspersed by low-intensity activities with brief recovery intervals (Mohr et al, 2005; Bradley et al, 2014). Young soccer players cover distances of 10–13 km throughout matches and achieve around. In addition to physical performance, soccer technical performance requires the progressive development of neuromuscular abilities in match-related power activities, such as sprinting and jumping (Barnes et al, 2014). It is necessary to better understand potential interference effects of concurrently performed power and endurance training to optimize players’ physiological adaptations over the soccer season using individualized training load data. This knowledge could be helpful to short- and long-term coaching decision-making (Barker and Armstrong, 2010; Álvarez-Kurogi et al, 2019)
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