Physiological Characteristics and Exhaustive Exercise Performance of Elite Soccer Players During a Season

The purpose of the study was to examine seasonal changes in high intensity exercise performance and physiological characteristics of elite soccer players. Eleven soccer players (24.0 ± 1.0 years, 179.7 ± 1.2 cm, 78.1 ± 1.6 kg and 58.5 ± 0.8 mlO2/min/kg (± SEM)) from a team in the best Danish soccer-league participated in the study. The players performed three submaximal running bouts (10, 14 and 17 km/h) and an incremental treadmill test to exhaustion on three separate occasions during the season: End-season (E; December), Pre-season; after a one-month season break (P; January) and Mid-season (M; July). Pulmonary oxygen uptake (VO2) and heart rate (HR) was measured continuously and blood samples were drawn frequently from an antecubital vein. Maximal oxygen uptake (VO2max) was higher (p < 0.05) at E and M compared to P (58.1 ± 0.9 and 59.0 ± 0.8 vs. 55.4 ± 0.7 mlO2/min/kg). In accordance, heart rates at 10, 14 and 17 km/h were lower (p < 0.05) at E and M compared to P (132 ± 4 and 128 ± 4 vs. 140 ± 5; 160 ± 5 and 158 ± 4 vs. 167 ± 3; 176 ± 3 and 175 ± 3 vs. 181 ± 3 beats/min, respectively). No differences were observed in HR or VO2 max between E and M. Time to exhaustion in the incremental test decreased (p < 0.05) from E to P (5.67 ± 0.18 to 5.45 ± 0.17 min), but reached 5.91 ± 0.12 min at M, which was higher (p < 0.05) than both E and P. Blood lactates at 10, 14 and 17 km/h were not significantly altered during the season, but peak lactates were higher (p < 0.05) at M compared to both E and P (9.8 ± 0.3 vs. 8.6 ± 0.7 and 8.9 ± 0.4 mM). The present study showed that high intensity exercise performance and physiological parameters fluctuates during a soccer season. The season break caused a marked decline in both aerobic power and exhaustive exercise performance. However, in mid-season maximal oxygen uptake was regained. Furthermore, peak blood lactates and performance of the exhaustive exercise test were higher in mid-season compared to end-season the previous year. This indicates that elite soccer players' ability to perform high intensity exercise is lowered towards the end of a season.