title: Hyperoxia does not accelerate quadriceps muscle deoxygenation kinetics at the onset of heavy exercise cycle.
abstract: OBJECTIVE
  The aim of this study was to determine whether an increase in O2 availability induces an alteration of the balance between O2 consumption ((V)O2) and O2 delivery ((Q)O2) at the muscle level. For that, we examined the effect of moderate hyperoxia on muscle deoxygenation kinetics at the onset of heavy-intensity cycling exercise.
  
  
  METHODS
  Eight young male adults performed step transitions from 35 W to heavy-intensity exercise corresponding to a power output half-way between the first ventilatory threshold and (V)O2max in normoxia and in hyperoxia (FIO2=0.30). Muscle deoxygenation (HHb) and total hemoglobin (Hbtot) were monitored continuously by near-infrared spectroscopy. HHb data were fit with a mono-exponential model from the onset of exercise up to 90 seconds.
  
  
  RESULTS
  Hyperoxia neither altered the delay before the increase in HHb (normoxia: 10.7±1.8 s vs. hyperoxia: 9.5±1.9 s; NS) nor the HHb mean response time (normoxia: 20.6±2.8 s vs. hyperoxia: 19.6±2.3 s; NS). Likewise, Hbtot was not different between normoxia and hyperoxia.
  
  
  CONCLUSIONS
  These results indicate that moderate hyperoxia has no effect on muscle deoxygenation kinetics at the onset of heavy exercise. It suggests that muscle (V)O2 increases at the same rate than O2 delivery when O2 availability is enhanced.
authors.affiliation: Laboratoire AMAPP, EA 4248, Université d'Orléans, Orléans, France. fabrice.prieur@univ-orleans.fr
authors.forename: F
authors.initials: F
authors.lastname: Prieur
authors.forename: G
authors.initials: G
authors.lastname: Dupont
authors.forename: N
authors.initials: N
authors.lastname: Blondel
authors.forename: P
authors.initials: P
authors.lastname: Mucci
mesh_terms: D000328:Adult; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D018496:Hyperoxia / Q000378:metabolism*; D008297:Male; D010100:Oxygen / Q000378:metabolism* / Q000493:pharmacokinetics; D010101:Oxygen Consumption; D005082:Physical Exertion; D052097:Quadriceps Muscle / Q000378:metabolism*; D055815:Young Adult
chemical_list: D006454:Hemoglobins; D010100:Oxygen