title: Systemic cytokine response following exercise-induced muscle damage in humans.
abstract: BACKGROUND
  Muscle adaptation which occurs following eccentric exercise-induced muscle damage has been associated with an acute inflammatory response. The purpose of this study was to investigate serum interleukin-6 (IL-6), osteoprotegerin and receptor activator of nuclear factor kB ligand (OPG/RANKL) concentrations following muscle damage. We measured changes for several days following muscle damage.
  
  
  METHODS
  Ten healthy young males performed an eccentric exercise protocol using their quadriceps. Blood samples were withdrawn before and at 6 h, 2 days, 5 days and 16 days post-exercise. Functional and clinical measurements were performed before, and on days 1, 2, 5, 8, 12 and 16 post-exercise.
  
  
  RESULTS
  The exercise protocol resulted in muscle damage, indicated by changes in biochemical markers. An increase in IL-6 and OPG, and a decrease in RANKL concentrations were seen at 6 h and on day 2 post-exercise; the OPG:RANKL ratio was increased at 6 h post-exercise (p < 0.05).
  
  
  CONCLUSIONS
  Changes in IL-6 and OPG/RANKL system may represent systemic responses in muscle inflammation and repair processes. However, further studies are needed to elucidate a potential systemic and/or local role of the OPG/RANKL system in skeletal muscle repair.
authors.affiliation: Department of Experimental Physiology, Medical School, National and Kapodistrian University of Athens, Goudi-Athens, Greece.
authors.forename: Anastassios
authors.initials: A
authors.lastname: Philippou
authors.forename: Gregory
authors.initials: G
authors.lastname: Bogdanis
authors.forename: Maria
authors.initials: M
authors.lastname: Maridaki
authors.forename: Antonis
authors.initials: A
authors.lastname: Halapas
authors.forename: Antigone
authors.initials: A
authors.lastname: Sourla
authors.forename: Michael
authors.initials: M
authors.lastname: Koutsilieris
mesh_terms: D000328:Adult; D015444:Exercise; D006801:Humans; D015850:Interleukin-6 / Q000097:blood*; D008297:Male; D018482:Muscle, Skeletal / Q000276:immunology* / Q000293:injuries*; D053244:Osteoprotegerin / Q000097:blood*; D053245:RANK Ligand / Q000097:blood*; D013997:Time Factors
chemical_list: D015850:Interleukin-6; D053244:Osteoprotegerin; D053245:RANK Ligand