title: Effect of training status and relative exercise intensity on physiological responses in men.
abstract: OBJECTIVE
  This study examined the effect of training status and relative exercise intensity on physiological responses to endurance exercise in humans.
  
  
  METHODS
  Seven endurance trained (TR: peak oxygen uptake [VO2peak] = 65.8 +/- 2.4 mL x kg(-1) min(-1)) and six untrained (UT: VO2peak = 46.2 +/- 1.9 mL x kg(-1) x min(-1)) men cycled for 60 min, either at a work rate corresponding to approximately 70% VO2peak or approximately 95% lactate threshold (LT).
  
  
  RESULTS
  The work rate and relative exercise intensity (i.e., % VO2peak) for UT 95% LT were lower (P < 0.01) than for all of the other trials. Although the work rate for UT 70% VO2peak was lower (P < 0.001) than for TR 70% VO2peak and TR 95% LT, average heart rate (HR) for the trial was higher (P < 0.01) throughout exercise in UT 70% VO2peak compared with all of the other trials. Plasma lactate and ammonia concentrations were greater (P < 0.01) during exercise in UT 70% VO2peak compared with all of the other trials. There was a tendency (P = 0.077) for plasma hypoxanthine to be greater at 60 min in UT 70% VO2peak compared with the other trials. At no time were any of the plasma metabolite concentrations different between the UT 95% LT, TR 95% LT and TR 70% VO2peak trials.
  
  
  CONCLUSIONS
  These data demonstrate that HR and plasma markers of metabolic stress were greater in UT compared with TR when exercise was performed at 70% VO2peak but were similar during exercise at 95% LT.
authors.affiliation: Department of Physiology, The University of Melbourne, Parkville, Victoria, Australia.
authors.forename: J
authors.initials: J
authors.lastname: Baldwin
authors.forename: R J
authors.initials: RJ
authors.lastname: Snow
authors.forename: M A
authors.initials: MA
authors.lastname: Febbraio
mesh_terms: D000328:Adult; D000641:Ammonia / Q000097:blood; D015415:Biomarkers / Q000097:blood; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008297:Male; D010101:Oxygen Consumption; D010807:Physical Endurance / Q000502:physiology*
chemical_list: D015415:Biomarkers; D019344:Lactic Acid; D000641:Ammonia