title: Training-related and competition-related risk factors for respiratory tract and gastrointestinal infections in elite cross-country skiers.
abstract: OBJECTIVE
  To examine symptoms indicative of respiratory tract and gastrointestinal infections and determine risk factors for such symptoms in elite cross-country skiers.
  
  
  METHODS
  Self-reported training and symptom data for 37 elite cross-country skiers from 2007 to 2015 were analysed using multilevel logistic regression equations with symptom incidence and duration as outcome variables, and sex, performance level, season, competition, air travel, altitude exposure and training characteristics as independent variables.
  
  
  RESULTS
  Data for 7016 person-weeks were analysed, including 464 self-reported infection events and 110 959 h of training. Athletes reported median (range) 3 (1-7) respiratory tract and/or gastrointestinal events per year, with symptoms lasting 5 (1-24) days. During the winter, symptoms occurred more frequently (OR 2.09, p<0.001) and lasted longer (b=0.043, p<0.001) compared with summer. Competition and air travel increased the risk of symptoms, with ORs of 2.93 (95% CI 2.24 to 3.83) and 4.94 (95% CI 3.74 to 6.53), respectively (p<0.001). Athletes with higher training monotony had lower risk of symptoms (OR 0.87 (95% CI 0.73 to 0.99), p<0.05). Other training variables were not associated with symptoms. Athletes who had won an Olympic/World Championship medal reported shorter symptom duration compared with less successful athletes (b=-0.019, p<0.05) resulting in significantly fewer symptomatic days/year (14 (6-29) vs 22 (8-43) days/year).
  
  
  CONCLUSIONS
  Air travel and competition are major risk factors for acute respiratory tract and gastrointestinal symptoms in this population. Athletes who have large fluctuations in training load experience such symptoms more frequently. Shorter duration of symptoms appears to be associated with success in cross-country skiing.
authors.affiliation: School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, UK.
authors.forename: Ida S
authors.initials: IS
authors.lastname: Svendsen
authors.affiliation: School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, UK.
authors.forename: Ian M
authors.initials: IM
authors.lastname: Taylor
authors.affiliation: Department of Training, Norwegian Olympic and Paralympic Committee and Confederation of Sports, Oslo, Norway.
authors.forename: Espen
authors.initials: E
authors.lastname: Tønnessen
authors.affiliation: Department of Training, Norwegian Olympic and Paralympic Committee and Confederation of Sports, Oslo, Norway Department of Sports Medicine, Oslo Sports Trauma Research Center, Norwegian School of Sport Sciences, Oslo, Norway.
authors.forename: Roald
authors.initials: R
authors.lastname: Bahr
authors.affiliation: School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, UK.
authors.forename: Michael
authors.initials: M
authors.lastname: Gleeson
mesh_terms: D000293:Adolescent; D000328:Adult; D000531:Altitude; D056352:Athletes; D005260:Female; D005767:Gastrointestinal Diseases / Q000453:epidemiology*; D006801:Humans; D015994:Incidence; D016015:Logistic Models; D008297:Male; D012141:Respiratory Tract Infections / Q000453:epidemiology*; D012189:Retrospective Studies; D012307:Risk Factors; D012621:Seasons; D012865:Skiing; D014195:Travel; D055815:Young Adult
keywords: Altitude; Athlete; Infection; Risk factor; Travel