Quantification of the physiological loading of one week of pre-season and one week of in-season training in professional soccer players

The aim of this study was to quantify the physiological loads of programmed pre-season and in-season training in professional soccer players. Data for players during each period were included for analysis (pre-season, n = 12; in-season, n = 10). We monitored physiological loading of training by measuring heart rate and rating of perceived exertion (RPE). Training loads were calculated by multiplying RPE score by the duration of training sessions. Each session was sub-categorized as physical, technical/tactical, physical and technical/tactical training. Average physiological loads in pre-season (heart rate 124 +/- 7 beats . min(-1); training load 4343 +/- 329 Borg scale . min) were higher compared with in-season (heart rate 112 +/- 7 beats . min(-1); training load 1703 +/- 173 Borg scale . min) (P < 0.05) and there was a greater proportion of time spent in 80-100% maximum heart rate zones (18 +/- 2 vs. 5 +/- 2%; P < 0.05). Such differences appear attributable to the higher intensities in technical/tactical sessions during pre-season (pre-season: heart rate 137 +/- 8 beats . min(-1); training load 321 +/- 23 Borg scale . min; in-season: heart rate 114 +/- 9 beats . min(-1); training load 174 +/- 27 Borg scale . min; P < 0.05). These findings demonstrate that pre-season training is more intense than in-season training. Such data indicate that these adjustments in load are a direct attempt to deliver training to promote specific training adaptations.