title: Exercise-induced oxidative stress in overload training and tapering.
abstract: Tapering can be an effective way of enhancing performance after a period of intensive training, but the mechanisms for this ergogenic effect are unclear. It was hypothesized that overload training will increase oxidative stress through an accumulative effect of repeated high-intensity exercise, whereas tapering will improve the antioxidant defense system and alleviate oxidative stress.
  
  
  OBJECTIVE
  To study the oxidative stress response to overload training and tapering.
  
  
  METHODS
  A group of eight well-trained male endurance athletes (30+/-6 yr; 73+/-13 kg; 64+/-6 mL.kg.min) performed two 4-wk periods of training in a crossover design. Each period included a 2-wk build-up phase followed either by 2 wk of training at the same load (control) or by a week with a 40% increase in training load (overload) preceding a week with a 60% reduction in training load (taper). Performance was monitored through weekly 15-min cycling time trials preceded by a 45-min preload at 70% Wmax. Blood samples were taken before and after the time trials and analyzed for oxidatively modified heme (OxHm), methemoglobin (metHb), and glutathione redox status.
  
  
  RESULTS
  Cycling time trials induced significant postexercise increases in levels of OxHm (+3.8%; P<0.001) and oxidized glutathione (GSSG: +13.9%; P<0.05) and decreases in metHb (-12.1%; P<0.001), reduced glutathione (GSH: -14.4%; P<0.001), and GSH/GSSG (-29.7%; P<0.001). Tapering was shown to significantly increase performance (+4.9%; P<0.05). Training modifications did not influence resting levels or exercise-induced changes of markers of oxidative stress.
  
  
  CONCLUSIONS
  A short period of tapered training improves performance but does not seem to be associated with substantial changes in exercise-induced oxidative stress.
authors.affiliation: Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, United Kingdom. n.vollaard@hw.ac.uk
authors.forename: Niels B J
authors.initials: NB
authors.lastname: Vollaard
authors.forename: Chris E
authors.initials: CE
authors.lastname: Cooper
authors.forename: Jerry P
authors.initials: JP
authors.lastname: Shearman
mesh_terms: D000975:Antioxidants; D018592:Cross-Over Studies; D005080:Exercise Test; D005978:Glutathione; D006801:Humans; D008297:Male; D018384:Oxidative Stress / Q000502:physiology*; D005082:Physical Exertion; D006113:United Kingdom
chemical_list: D000975:Antioxidants; D005978:Glutathione