title: Exercise-induced muscle damage, plasma cytokines, and markers of neutrophil activation.
abstract: BACKGROUND
  Unaccustomed eccentric exercise often results in muscle damage and neutrophil activation. We examined changes in plasma cytokines stress hormones, creatine kinase activity and myoglobin concentration, neutrophil surface receptor expression, degranulation, and the capacity of neutrophils to generate reactive oxygen species in response to in vitro stimulation after downhill running.
  
  
  METHODS
  Ten well-trained male runners ran downhill on a treadmill at a gradient of -10% for 45 min at 60% VO2max. Blood was sampled immediately before (PRE) and after (POST), 1 h (1 h POST), and 24 h (24 h POST) after exercise.
  
  
  RESULTS
  At POST, there were significant increases (P < 0.01) in neutrophil count (32%), plasma interleukin (IL)-6 concentration (460%), myoglobin (Mb) concentration (1100%), and creatine kinase (CK) activity (40%). At 1 h POST, there were further increases above preexercise values for neutrophil count (85%), plasma Mb levels (1800%), and CK activity (56%), and plasma IL-6 concentration remained above preexercise values (410%) (P < 0.01). At 24 h POST, neutrophil counts and plasma IL-6 levels had returned to baseline, whereas plasma Mb concentration (100%) and CK activity (420%) were elevated above preexercise values (P < 0.01). There were no significant changes in neutrophil receptor expression, degranulation and respiratory burst activity, and plasma IL-8 and granulocyte-colony stimulating factor concentrations at any time after exercise. Neutrophil count correlated with plasma Mb concentration at POST (r = 0.64, P < 0.05), and with plasma CK activity at POST (r = 0.83, P < 0.01) and 1 h POST (r = 0.78, P < 0.01).
  
  
  CONCLUSIONS
  Neutrophil activation remains unchanged after downhill running in well-trained runners, despite increases in plasma markers of muscle damage.
authors.affiliation: School of Human Movement Studies, University of Queensland, St. Lucia, Brisbane, Queensland, Australia.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Peake
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Suzuki
authors.forename: Gary
authors.initials: G
authors.lastname: Wilson
authors.forename: Matthew
authors.initials: M
authors.lastname: Hordern
authors.forename: Kazunori
authors.initials: K
authors.lastname: Nosaka
authors.forename: Laurel
authors.initials: L
authors.lastname: Mackinnon
authors.forename: Jeff S
authors.initials: JS
authors.lastname: Coombes
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000378:metabolism; D003402:Creatine Kinase / Q000097:blood; D004837:Epinephrine / Q000097:blood; D013006:Growth Hormone / Q000097:blood; D006801:Humans; D015850:Interleukin-6 / Q000097:blood*; D007958:Leukocyte Count; D008297:Male; D018482:Muscle, Skeletal / Q000293:injuries* / Q000378:metabolism*; D009211:Myoglobin / Q000097:blood; D018375:Neutrophil Activation / Q000502:physiology*; D009504:Neutrophils / Q000378:metabolism; D009638:Norepinephrine / Q000097:blood; D012420:Running; D013997:Time Factors
chemical_list: D015415:Biomarkers; D015850:Interleukin-6; D009211:Myoglobin; D013006:Growth Hormone; D003402:Creatine Kinase; D009638:Norepinephrine; D004837:Epinephrine