Journal of Applied Physiology Fuel your research with LabChart
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

J Appl Physiol 94: 2181-2187, 2003. First published November 27, 2002; doi:10.1152/japplphysiol.00866.2002
8750-7587/03 $5.00
This Article
Right arrow Full Text Free
Right arrow Full Text (PDF) Free
Right arrow All Versions of this Article:
94/6/2181    most recent
00866.2002v1
Right arrow Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via ISI Web of Science (23)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Baldwin, J.
Right arrow Articles by Febbraio, M. A.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Baldwin, J.
Right arrow Articles by Febbraio, M. A.
Vol. 94, Issue 6, 2181-2187, June 2003

Glycogen availability does not affect the TCA cycle or TAN pools during prolonged, fatiguing exercise

Jacinta Baldwin1, Rodney J. Snow2, Martin J. Gibala3, Andrew Garnham2, Krista Howarth3, and Mark A. Febbraio1,4

1 Department of Physiology, University of Melbourne, Parkville 3010, Victoria; 2 School of Health Sciences, Deakin University, Burwood 3125, Victoria; 4 Skeletal Muscle Research Laboratory, School of Medical Sciences, Royal Melbourne Institute of Technology, Bundoora 3083, Victoria, Australia; and 3 Exercise Metabolism Research Group, Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada L8S4K1

The hypothesis that fatigue during prolonged exercise arises from insufficient intramuscular glycogen, which limits tricarboxylic acid cycle (TCA) activity due to reduced TCA cycle intermediates (TCAI), was tested in this experiment. Seven endurance-trained men cycled at ~70% of peak O2 uptake (VO2 peak) until exhaustion with low (LG) or high (HG) preexercise intramuscular glycogen content. Muscle glycogen content was lower (P < 0.05) at fatigue than at rest in both trials. However, the increase in the sum of four measured TCAI (>70% of the total TCAI pool) from rest to 15 min of exercise was not different between trials, and TCAI content was similar after 103 ± 15 min of exercise (2.62 ± 0.31 and 2.59 ± 0.28 mmol/kg dry wt for LG and HG, respectively), which was the point of volitional fatigue during LG. Subjects cycled for an additional 52 ± 9 min during HG, and although glycogen was markedly reduced (P < 0.05) during this period, no further change in the TCAI pool was observed, thus demonstrating a clear dissociation between exercise duration and the size of the TCAI pool. Neither the total adenine nucleotide pool (TAN = ATP + ADP + AMP) nor IMP was altered compared with rest in either trial, whereas creatine phosphate levels were not different when values measured at fatigue were compared with those measured after 15 min of exercise. These data demonstrate that altered glycogen availability neither compromises TCAI pool expansion nor affects the TAN pool or creatine phosphate or IMP content during prolonged exercise to fatigue. Therefore, our data do not support the concept that a decrease in muscle TCAI during prolonged exercise in humans compromises aerobic energy provision or is the cause of fatigue.

citric acid cycle; metabolic stress; hypoxanthine


This article has been cited by other articles:


Home page
 Br. J. Sports. Med.Home page
T D Noakes
Rating of perceived exertion as a predictor of the duration of exercise that remains until exhaustion
Br. J. Sports Med., July 1, 2008; 42(7): 623 - 624.
[Full Text] [PDF]

Home page
 DiabetesHome page
D. J. Baker, P. L. Greenhaff, A. MacInnes, and J. A. Timmons
The Experimental Type 2 Diabetes Therapy Glycogen Phosphorylase Inhibition Can Impair Aerobic Muscle Function During Prolonged Contraction
Diabetes, June 1, 2006; 55(6): 1855 - 1861.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Endocrinol. Metab.Home page
R. C. Camacho, E. P. Donahue, F. D. James, E. D. Berglund, and D. H. Wasserman
Energy state of the liver during short-term and exhaustive exercise in C57BL/6J mice
Am J Physiol Endocrinol Metab, March 1, 2006; 290(3): E405 - E408.
[Abstract] [Full Text] [PDF]

Home page
 J. Appl. Physiol.Home page
T. D. Noakes, R. J. Snow, and M. A. Febbraio
Linear relationship between the perception of effort and the duration of constant load exercise that remains
J Appl Physiol, April 1, 2004; 96(4): 1571 - 1573.
[Full Text] [PDF]


HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Visit Other APS Journals Online
Copyright © 2003 by the American Physiological Society.