| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Received October 29, 2002
Accepted after revision March 3, 2003
1 Institute of Exercise and Sports Sciences, August Krogh Institute, Department of Human Physiology, University of Copenhagen, Denmark
2 Applied Physiology Group, Strathclyde Institute for Biomedical Sciences, University of Strathclyde, Glasgow, UK
3 Sports Medicine Research Unit, Department of Rheumatology H, Bispebjerg Hospital, Copenhagen, Denmark
4 August Krogh Institute, Copenhagen Muscle Research Centre, Universitetsparken 13, DK-2100 Copenhagen Ò, Denmark
* To whom correspondence should be addressed. E-mail: jbangsbo{at}aki.ku.dk.
The aim of the present study was to simultaneously examine skeletal muscle heat production and ATP turnover in humans during dynamic exercise with marked differences in aerobic metabolism. This was done to test the hypothesis that efficiency is higher in anaerobic than aerobic ATP resynthesis. Six healthy male subjects performed 90 s of low intensity knee-extensor exercise with (OCC) and without thigh occlusion (CON-LI) as well as 90 s of high intensity exercise (CON-HI) that continued from the CON-LI bout. Muscle heat production was determined by continuous measurements of muscle heat accumulation and heat release to the blood. Muscle ATP production was quantified by repeated measurements of thigh oxygen uptake as well as blood and muscle metabolite changes. All temperatures of the thigh were equalized to ~37 °C prior to exercise by a water-perfused heating cuff. Oxygen uptake accounted for 81 ± 6 and 58 ± 8 %, respectively, of the total ATP resynthesis in CON-LI and CON-HI, whereas it was negligible in OCC. The rise in muscle temperature was lower (P < 0.05) in OCC than CON-LI (0.32 ± 0.04 vs. 0.37 ± 0.03 °C). The rate of heat production was also lower (P < 0.05) in OCC than CON-LI (36 ± 4 vs. 57 ± 4 J s-1). Mechanical efficiency was 52 ± 4 % after 15 s of OCC and remained constant, whereas it decreased (P < 0.05) from 56 ± 5 to 32 ± 3 % during CON-LI. During CON-HI, mechanical efficiency transiently increased (P < 0.05) to 47 ± 4 %, after which it decreased (P < 0.05) to 36 ± 3 % at the end of CON-HI. Assuming a fully coupled mitochondrial respiration, the ATP turnover per unit of work was calculated to be unaltered during OCC (~20 mmol ATP kJ-1), whereas it increased (P < 0.05) from 21 ± 4 to 29 ± 3 mmol ATP kJ-1 during CON-LI and further (P < 0.05) to 37 ± 3 mmol ATP kJ-1 during CON-HI. The present data confirm the hypothesis that heat loss is lower in anaerobic ATP resynthesis than in oxidative phosphorylation and can in part explain the finding that efficiency declines markedly during dynamic exercise. In addition, the rate of ATP turnover apparently increases during constant load low intensity exercise. Alternatively, mitochondrial efficiency is lowered as exercise progresses, since ATP turnover was unaltered during the ischaemic exercise bout.
This article has been cited by other articles:
|
|
 |
|
  S. P. Mortensen, R. Damsgaard, E. A. Dawson, N. H. Secher, and J. Gonzalez-Alonso Restrictions in systemic and locomotor skeletal muscle perfusion, oxygen supply and VO2 during high-intensity whole-body exercise in humans J. Physiol., May 15, 2008; 586(10): 2621 - 2635. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. Bishop, J. Edge, C. Thomas, and J. Mercier High-intensity exercise acutely decreases the membrane content of MCT1 and MCT4 and buffer capacity in human skeletal muscle J Appl Physiol, February 1, 2007; 102(2): 616 - 621. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
I. R. Lanza, D. M. Wigmore, D. E. Befroy, and J. A. Kent-Braun In vivo ATP production during free-flow and ischaemic muscle contractions in humans J. Physiol., November 15, 2006; 577(1): 353 - 367. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. A. Ferguson, P. Krustrup, M. Kjaer, M. Mohr, D. Ball, and J. Bangsbo Effect of temperature on skeletal muscle energy turnover during dynamic knee-extensor exercise in humans J Appl Physiol, July 1, 2006; 101(1): 47 - 52. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 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]
|
|
|
|
 |
|
 S. R. Gray, G. De Vito, M. A. Nimmo, D. Farina, and R. A. Ferguson Skeletal muscle ATP turnover and muscle fiber conduction velocity are elevated at higher muscle temperatures during maximal power output development in humans Am J Physiol Regulatory Integrative Comp Physiol, February 1, 2006; 290(2): R376 - R382. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. Sahlin, J. B. Sorensen, L. B. Gladden, H. B. Rossiter, and P. K. Pedersen Prior heavy exercise eliminates VO2 slow component and reduces efficiency during submaximal exercise in humans J. Physiol., May 1, 2005; 564(3): 765 - 773. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. Krustrup, Y. Hellsten, and J. Bangsbo Intense interval training enhances human skeletal muscle oxygen uptake in the initial phase of dynamic exercise at high but not at low intensities J. Physiol., August 15, 2004; 559(1): 335 - 345. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. W. Scheuermann and T. J. Barstow O2 uptake kinetics during exercise at peak O2 uptake J Appl Physiol, November 1, 2003; 95(5): 2014 - 2022. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH |
