title: Oxidative stress in half and full Ironman triathletes.
abstract: BACKGROUND
  Ultraendurance athletes who maintain a very high volume of exercise may, as a result of greater production of reactive oxygen species (ROS), be particularly susceptible to oxidative damage.
  
  
  OBJECTIVE
  This study sought to examine and compare pre- and postrace markers of oxidative stress in ultraendurance athletes training for, and competing in, either a half or a full Ironman triathlon.
  
  
  METHODS
  Resting and postexercise blood was sampled from 16 half Ironman triathletes, 29 full Ironman triathletes, and age-matched, relatively inactive controls. Blood was analyzed for markers of oxidative stress (malondialdehyde (MDA) concentration) and antioxidant status (glutathione peroxidase (GPX), catalase (CAT), and superoxide dismutase (SOD) activities).
  
  
  RESULTS
  Compared with controls, the half Ironman triathletes had significantly (P < 0.001) higher erythrocyte GPX activity at rest, whereas the Ironman triathletes had significantly (P < 0.05) lower resting plasma MDA and significantly (P < 0.05) greater resting activities of GPX and CAT compared with controls. As a result of the half Ironman triathlon, there was a significant (P < 0.05) increase in MDA and significant (P < 0.05) decreases in erythrocyte GPX, SOD, and CAT activities. These changes also occurred in response to the Ironman triathlon; MDA significantly (P < 0.05) increased, and there were significant (P < 0.001) decreases in GPX, CAT, and SOD activities. Users of antioxidant supplements in both the half and full Ironman races had significantly (P < 0.05) elevated MDA after races compared with nonsupplementers.
  
  
  CONCLUSIONS
  The present investigation indicates that training for and competing in half and full Ironman triathlons has different effects on erythrocyte antioxidant enzyme activities and oxidative stress.
authors.affiliation: Institute of Sport and Exercise Science, James Cook University, Cairns, Queensland, Australia. wade.knez@jcu.edu.au
authors.forename: Wade L
authors.initials: WL
authors.lastname: Knez
authors.forename: David G
authors.initials: DG
authors.lastname: Jenkins
authors.forename: Jeff S
authors.initials: JS
authors.lastname: Coombes
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000328:Adult; D000975:Antioxidants; D001642:Bicycling / Q000502:physiology*; D016022:Case-Control Studies; D004912:Erythrocytes / Q000378:metabolism*; D005260:Female; D005979:Glutathione Peroxidase / Q000096:biosynthesis; D006801:Humans; D008297:Male; D008315:Malondialdehyde; D009119:Muscle Contraction / Q000502:physiology*; D018384:Oxidative Stress / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D012307:Risk Factors; D012420:Running / Q000502:physiology*; D013177:Sports; D013482:Superoxide Dismutase / Q000096:biosynthesis; D013550:Swimming / Q000502:physiology*; D013997:Time Factors
chemical_list: D000975:Antioxidants; D008315:Malondialdehyde; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase