title: Seasonal variation in fitness variables in professional soccer players.
abstract: 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.
authors.affiliation: EGB Zaragoza, Universidad de Zaragoza, Medical Sport Center of Government of Aragon, Zaragoza, Spain. joseant@posta.unizar.es
authors.forename: J A
authors.initials: JA
authors.lastname: Casajús
mesh_terms: D000328:Adult; D015308:Anaerobic Threshold / Q000502:physiology*; D000886:Anthropometry; D015444:Exercise / Q000502:physiology*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology*; D010809:Physical Fitness / Q000502:physiology*; D012916:Soccer / Q000502:physiology*