Muscle IMP accumulation during fatiguing submaximal exercise in endurance trained and untrained men.
To examine the effect of training status on muscle metabolism during exercise, seven endurance-trained [peak oxygen uptake (VO(2 peak)) = 65.8 +/- 2.4 ml. kg(-1). min(-1)] and six untrained (VO(2 peak) = 46. 2 +/- 1.9 ml. kg(-1). min(-1)) men cycled to fatigue at a work rate calculated to require 70% VO(2 peak). Time to exhaustion was 36% longer (P < 0.01) in trained (TR) compared with untrained (UT) men (148 +/- 11 vs. 95 +/- 8 min). Although intramuscular glycogen content was reduced (P < 0.05) in both TR and UT at fatigue, IMP, a marker of a mismatch between ATP supply and demand, was only elevated (P < 0.01) in UT muscle at fatigue and was approximately fourfold higher at this point in UT compared with TR. These data demonstrate that fatiguing submaximal exercise was associated with a similar low level of intramuscular glycogen in both TR and UT men, but a mismatch between ATP supply and demand only occurred in UT individuals.
Baldwin
J
J
Exercise Physiology and Metabolism Laboratory, Department of Physiology, The University of Melbourne, Parkville, 3052 Victoria, Australia.
Snow
R J
RJ
Carey
M F
MF
Febbraio
M A
MA
D000328:Adult; D015444:Exercise / Q000502:physiology*; D006801:Humans; D007291:Inosine Monophosphate / Q000378:metabolism*; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism; D010807:Physical Endurance / Q000502:physiology*
D007291:Inosine Monophosphate