title: Effects of maximal static apnea on antioxidant defenses in trained free divers.
abstract: OBJECTIVE
  To investigate the effects of maximal static apnea on plasma antioxidant status, oxidative stress, and antioxidant enzyme activities in trained free divers.
  
  
  METHODS
  Blood was taken from apnea-trained (Tr) and control (Con) subjects at baseline (B) and after one (A1), three (A3), and five (A5) apneas. Trolox equivalent antioxidant capacity (TEAC), ferric reducing ability of plasma (FRAP), uric acid, and bilirubin assays assessed plasma antioxidant status and malondialdehyde (MDA) quantified the oxidative stress response. The activities of erythrocyte antioxidant enzymes superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) were determined at baseline and after the fifth apnea.
  
  
  RESULTS
  TEAC was significantly higher in divers versus controls after A1 (P < 0.05). A group effect of SOD activity indicated higher activity throughout the protocol in Tr (mean +/- SD; Con, 43.2 +/- 10.1 U.g Hb; Tr, 50.1 +/- 7.3 U.g Hb; P = 0.04). With no other group differences, the groups' data were combined. Apnea significantly increased SOD (B, 44.1 +/- 11.1 U.g Hb; A5, 48.1 +/- 7.5 U.g Hb; P < 0.05) and GPx activity (B, 60.5 +/- 14.9 U.g Hb; A5, 70.1 +/- 16.0 U.g Hb; P = 0.02); however, CAT activity decreased (B, 5.25 +/- 0.59 U.mg Hb; A5, 5.00 +/- 0.53 U.mg Hb; P = 0.03). MDA was unaffected by apnea (P = 0.32).
  
  
  CONCLUSIONS
  Trained free divers have increased SOD activity during apnea; however, there is little difference in their antioxidant and oxidative stress responses compared with controls. In both groups, acute changes in antioxidant enzyme activities suggest that they may protect from excessive antioxidant depletion and oxidative stress during apnea.
authors.affiliation: School of Human Movement Studies, University of Queensland, Brisbane, AUSTRALIA.
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Bulmer
authors.forename: Jeff S
authors.initials: JS
authors.lastname: Coombes
authors.forename: James E
authors.initials: JE
authors.lastname: Sharman
authors.forename: Ian B
authors.initials: IB
authors.lastname: Stewart
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D000704:Analysis of Variance; D001049:Apnea / Q000097:blood / Q000150:complications*; D016022:Case-Control Studies; D002374:Catalase / Q000097:blood; D004242:Diving / Q000009:adverse effects / Q000502:physiology*; D004912:Erythrocytes / Q000201:enzymology; D005260:Female; D005609:Free Radicals; D005978:Glutathione / Q000097:blood; D005979:Glutathione Peroxidase / Q000097:blood; D006339:Heart Rate; D006801:Humans; D000860:Hypoxia / Q000097:blood / Q000150:complications; D008297:Male; D008315:Malondialdehyde / Q000097:blood; D018384:Oxidative Stress; D010100:Oxygen / Q000097:blood*; D017382:Reactive Oxygen Species; D013482:Superoxide Dismutase / Q000097:blood
chemical_list: D005609:Free Radicals; D017382:Reactive Oxygen Species; D008315:Malondialdehyde; D002374:Catalase; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase; D005978:Glutathione; D010100:Oxygen