title: Injury risk in professional football players with special reference to the playing position and training periodization.
abstract: OBJECTIVE
  The aim of this study was to examine injury incidence in professional football players according to the playing positions and with a special reference to training periodization.
  
  
  METHODS
  A Spanish professional team was followed prospectively for the 2007-08 and 2008-09 seasons and exposure times and time-loss injuries were individually recorded during all training sessions and matches. Heart rate was monitored in all training sessions.
  
  
  RESULTS
  total of 114 injuries were registered during the study period (mean injury incidence: 6.6 injuries per 1000 hours). The frequency of injuries was not uniformly distributed by playing positions (P<0.001), as forwards and central defenders sustained the greatest number of injury episodes and the highest match absence. Ligament sprains and muscle strains accounted for 50% of all injuries and 62% of all match absences. The highest incidence of sprains was achieved during pre-season and the beginning of the competition period. The risk to sustain a muscular strain peaked at the beginning and in the final weeks of the competition period and was related (r=0.72; P<0.05) to mean heart rate during the training stage.
  
  
  CONCLUSIONS
  The results suggest that there exists a difference of injury risk according to the period of the season and therefore, injury prevention strategies should be introduced from pre-season. Moreover, training workloads should be controlled to avoid increasing the risk of muscle strains.
authors.affiliation: Sports Department, Faculty of Physical Activity and Sport, Technical University of Madrid, Madrid, Spain. javier.mallo@upm.es
authors.forename: J
authors.initials: J
authors.lastname: Mallo
authors.forename: Alexandre
authors.initials: A
authors.lastname: Dellal
mesh_terms: D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D015601:Injury Severity Score; D008297:Male; D018482:Muscle, Skeletal / Q000293:injuries*; D010806:Physical Education and Training / Q000379:methods*; D012189:Retrospective Studies; D012307:Risk Factors; D012916:Soccer / Q000293:injuries*; D013180:Sprains and Strains / Q000175:diagnosis / Q000453:epidemiology*; D014416:Tunisia / Q000453:epidemiology; D055815:Young Adult