title: Cytokine responses to treadmill running in healthy and illness-prone athletes.
abstract: OBJECTIVE
  To characterize differences in cytokine responses to exercise of different intensities and durations between healthy and illness-prone runners.
  
  
  METHODS
  Trained distance runners were classified as healthy (no more than two episodes of upper-respiratory symptoms per year; N = 10) or illness-prone (four or more episodes per year; N = 8) and completed three treadmill tests: SHORT (30 min, 65% VO2max), LONG (60 min, 65% VO2max), and INTENSE (6 x 3 min, 90% VO2max). Blood samples were collected pre-, post-, 1 h, 10 h, and 24 h after exercise, and interleukin (IL)-2, IL-4, IL-6, IL-8, IL-10, IL-12, and IL-1ra concentrations were determined. Repeated-measures ANOVA was used to assess changes in cytokine responses to exercise. Magnitudes of changes and differences between groups were characterized using Cohen's effect size (ES) criteria.
  
  
  RESULTS
  Resting IL-8, IL-10, and IL-1ra concentrations were 19-38% lower (ES:0.38-0.96; small to moderate differences) in illness-prone runners. Similarly, postexercise IL-10 concentrations were 13-20% lower (ES: 0.20-0.37; small differences), and IL-1ra concentrations were 10-20% lower (ES: 0.22-0.38; small differences) in illness-prone subjects. In contrast, IL-6 elevations were 84-185% higher (ES: 0.29-0.59, small differences) in illness-prone subjects. Postexercise responses of IL-2, IL-4, and IL-12 were small and not substantially different between the groups.
  
  
  CONCLUSIONS
  Cytokine responses to controlled treadmill running differ between healthy and illness-prone athletes. Illness-prone distance runners showed evidence suggestive of impaired inflammatory regulation in the hours after exercise that may account for the greater frequency of upper-respiratory symptoms experienced.
authors.affiliation: Department of Physiology, Australian Institute of Sport, Canberra, Australia. amanda.cox@ausport.gov.au
authors.forename: Amanda Julie
authors.initials: AJ
authors.lastname: Cox
authors.forename: David Bruce
authors.initials: DB
authors.lastname: Pyne
authors.forename: Philo Urson
authors.initials: PU
authors.lastname: Saunders
authors.forename: Robin
authors.initials: R
authors.lastname: Callister
authors.forename: Maree
authors.initials: M
authors.lastname: Gleeson
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D016207:Cytokines / Q000097:blood*; D004198:Disease Susceptibility; D005080:Exercise Test; D006801:Humans; D008297:Male; D012141:Respiratory Tract Infections / Q000097:blood*; D012420:Running; D013177:Sports; D014481:United States
chemical_list: D016207:Cytokines