Effect of training status and relative exercise intensity on physiological responses in men.
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.
Baldwin
J
J
Department of Physiology, The University of Melbourne, Parkville, Victoria, Australia.
Snow
R J
RJ
Febbraio
M A
MA
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*
D015415:Biomarkers; D019344:Lactic Acid; D000641:Ammonia