title: Endurance exercise, plasma oxidation and cardiovascular risk.
abstract: OBJECTIVE
  Although physical activity is beneficial to health, people who exercise at high intensities throughout their lifetime may have increased cardiovascular risk. Aerobic exercise increases oxidative stress and may contribute to atherogenesis by augmented oxidation of plasma lipoproteins. The aim of this study was to examine the relationship between aerobic power and markers of oxidative stress, including the susceptibility of plasma to oxidation.
  
  
  RESULTS
  Aerobic power was measured in 24 healthy men aged 29+/-9 years (mean+/-SD). Plasma was analysed from subjects of high aerobic power (HAP; VO2max, 64.6+/-6.1 ml/kg/min) and lower aerobic power (LAP;VO2max, 45.1+/-6.3 ml/kg/min) for total antioxidant capacity (TAC), malondialdehyde (MDA) and susceptibility to oxidation. Three measures were used to quantify plasma oxidizability: (1) lag time to conjugated diene formation (lag time); (2) change in absorbance at 234 nm and; (3) slope of the oxidation curve during propagation (slope). The HAP subjects had significantly lower TAC (1.38+/-0.04 versus 1.42+/-0.06 TEAC units; P < 0.05), significantly higher change in absorbance (1.55+/-0.21 versus 1.36+/-0.17 arbitrary units; P < 0.05), but no difference in MDA (P = 0.6), compared to LAP subjects. There was a significant inverse association between TAC and slope (r = -0.49; P < 0.05). Lipoprotein profiles and daily intake of nutrients did not differ between the groups.
  
  
  CONCLUSIONS
  These findings suggest that people with high aerobic power, due to extreme endurance exercise, have plasma with decreased antioxidant capacity and higher susceptibility to oxidation, which may increase their cardiovascular risk.
authors.affiliation: The University of Tasmania, Centre for Human Movement, Launceston, Australia. jsharman@soms.uq.edu.au
authors.forename: James E
authors.initials: JE
authors.lastname: Sharman
authors.forename: Dominic P
authors.initials: DP
authors.lastname: Geraghty
authors.forename: Cecilia M
authors.initials: CM
authors.lastname: Shing
authors.forename: David I
authors.initials: DI
authors.lastname: Fraser
authors.forename: Jeff S
authors.initials: JS
authors.lastname: Coombes
mesh_terms: D000293:Adolescent; D000328:Adult; D002318:Cardiovascular Diseases / Q000097:blood / Q000453:epidemiology / Q000378:metabolism; D017079:Exercise Tolerance / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D018384:Oxidative Stress; D012307:Risk Factors