Background: There have been many studies on soccer, but few evaluations of the physiological function of professional soccer players. The aim of this work was to evaluate seasonal variation--from September to February--in anthropometric and physiological variables in a Spanish professional soccer team (n=15).
Methods: Anthropometric measurements were obtained following the standardised techniques adopted by the International Society for the Advancement of Kinanthropometry (ISAK). A maximal treadmill test with breath-by-breath gas analysis was carried out to evaluate the aerobic condition and a Jump test was used to measure muscle performance and strength in the lower limbs.
Results: There were no significant variations in body mass, although a statistically significant decrease (p<0.05) in fat percentage and sum of six skinfolds was observed. The somatotype (Heath-Carter) was mesomorphic without any change observed throughout the season. The mean VO2max in the first test (65.5 ml x kg(-1) x min(-1)) had not changed by the second one (66.4 ml x kg(-1) x min(-1)). There were no significant differences in maximal heart rate (185 vs 185 beats x min(-1)) and treadmill speed at VO2max (16.1 vs 15.8 km x h(-1)). At the anaerobic threshold, there were significant differences (p<0.05) in speed (12.4 vs 13.1 km x h(-1)) and heart rate (164 vs 168 beats x min(-1)) as the season progressed. When the data were expressed as a percentage of maximal values obtained, we observed that the speed in the first test was 77 and 83% in the second test. For heart rate, values were 89 and 91%, and for oxygen uptake 77 and 79%. The Jump test did not show any significant change during the season.
Conclusions: We can conclude from these results that professional soccer players have good fitness from the beginning of the Spanish League--with a high VO2max--and the changes observed depend on the initial values.