title: Effect of endurance training on the VO2-work rate relationship in normoxia and hypoxia.
abstract: OBJECTIVE
  We postulated that the relationship between VO2 and work rate (VO2-WR relationship) during incremental exercise is dependent on O2 availability, and that training-induced adaptations alter this relationship. We therefore studied the effect of endurance training on VO2 response during incremental exercise in normoxia and hypoxia (FIO2=0.134).
  
  
  METHODS
  Before and after training (6 d.wk, 4 wk), eight subjects performed incremental exercises under normoxia and hypoxia and one constant-work rate exercise in normoxia at 80% of pretraining VO2max. The slopes of the VO2-WR relationship during incremental exercise were calculated using all the points (whole slope) or only points before the lactate threshold (pre-LT slope). The difference between VO2max measured and VO2max expected from the pre-LT slope (DeltaVO2) was determined, as was the difference between VO2 at minute 10 and VO2 at minute 4 during the constant-work rate exercise (DeltaVO2(10'-4')).
  
  
  RESULTS
  In normoxia, training induced a significant decrease in the whole slope (11.0+/-1.0 vs 9.9+/-0.4 mL.min.W, P<0.05). In hypoxia, training induced a significant increase in the pre-LT slope (8.7+/-1.2 vs 9.8+/-0.7 mL.min.W; P<0.05) and the whole slope (8.5+/-1.2 vs 9.4+/-0.5 mL.min.W; P<0.05). A significant correlation between the decrease of DeltaVO2 and the decrease of DeltaVO2(10'-4') with training was found in normoxia (P<0.01, r=0.79).
  
  
  CONCLUSIONS
  Taken together, these results indicate that adaptations induced by endurance training are associated with more efficient incremental and constant-workload exercise performed in normoxia. Moreover, training contributes to improved O2 delivery during moderate exercise performed in hypoxia, and to enhanced near-maximal exercise tolerance.
authors.affiliation: Laboratory of Multidisciplinary Analysis in Physical Activities, UFR STAPS of Lievin, University of Artois, Lievin, FRANCE. fabrice.prieur@worldonline.fr
authors.forename: Fabrice
authors.initials: F
authors.lastname: Prieur
authors.forename: Henri
authors.initials: H
authors.lastname: Benoit
authors.forename: Thierry
authors.initials: T
authors.lastname: Busso
authors.forename: Josiane
authors.initials: J
authors.lastname: Castells
authors.forename: Christian
authors.initials: C
authors.lastname: Denis
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D005080:Exercise Test; D005260:Female; D006339:Heart Rate; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D008176:Lung Volume Measurements; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*; D010809:Physical Fitness / Q000502:physiology*