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1 Biology Department, University of Ottawa, Ottawa, Ontario, Canada
2 Defence R&D Canada, Ottawa, Ontario, Canada
3 School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
4 School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada; Defence R&D Canada, Toronto, Ontario, Canada
* To whom correspondence should be addressed. E-mail: JMWEBER{at}science.uottawa.ca.
The purpose of this study was to quantify how shivering activity would be affected by large changes in fuel metabolism (see Haman et al., submitted). Adult men were exposed to 10°C for 2-h after a low-carbohydrate diet and exercise (LO) and after high-carbohydrate diet without exercise (HI). Using simultaneous metabolic and electromyographic (EMG) measurements, the effects of changes in fuel selection on the shivering activity of 8 large muscles representing >90% of total shivering muscle mass were quantified. Contrary to expectation, drastic changes in fuel metabolism (carbohydrates 28 vs 65% of total heat production (Hprod), lipids 52 vs 23%Hprod and proteins 19 vs 12% Hprod for LO and HI, respectively) are achieved without altering the EMG signature of shivering muscles. Results show that total shivering activity and the specific contribution of each muscle to total shivering activity are not affected by large changes in fuel selection. In addition, we found that changes in burst shivering rate (~4 burst.min-1), relative contribution of burst activity to total shivering (~10% of total shivering activity), and burst shivering intensity (~12% of maximal voluntary contraction) are the same between LO and HI. Spectral analysis of EMG signals also reveal that mean frequencies of the power spectrum remained the same under all conditions (whole body average of 78±5 Hz for LO and 83±7 Hz for HI). During low-intensity shivering, humans are therefore able to sustain thermogenic rate by oxidizing widely different fuel mixtures within the same muscle fibers.
This article has been cited by other articles:
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  E. Vaillancourt, F.ço. Haman, and J.-M. Weber Fuel selection in Wistar rats exposed to cold: shivering thermogenesis diverts fatty acids from re-esterification to oxidation J. Physiol., September 1, 2009; 587(17): 4349 - 4359. [Abstract] [Full Text] [PDF]
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 F. Haman, C. G. Scott, and G. P. Kenny Fueling shivering thermogenesis during passive hypothermic recovery J Appl Physiol, October 1, 2007; 103(4): 1346 - 1351. [Abstract] [Full Text] [PDF]
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F. Haman Shivering in the cold: from mechanisms of fuel selection to survival J Appl Physiol, May 1, 2006; 100(5): 1702 - 1708. [Abstract] [Full Text] [PDF]
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F. Haman, F. Peronnet, G. P Kenny, D. Massicotte, C. Lavoie, and J.-M. Weber Partitioning oxidative fuels during cold exposure in humans: muscle glycogen becomes dominant as shivering intensifies J. Physiol., July 1, 2005; 566(1): 247 - 256. [Abstract] [Full Text] [PDF]
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F. Haman, S. R. Legault, and J.-M. Weber Fuel selection during intense shivering in humans: EMG pattern reflects carbohydrate oxidation J. Physiol., April 1, 2004; 556(1): 305 - 313. [Abstract] [Full Text] [PDF]
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F. Haman, F. Peronnet, G. P. Kenny, E. Doucet, D. Massicotte, C. Lavoie, and J.-M. Weber Effects of carbohydrate availability on sustained shivering I. Oxidation of plasma glucose, muscle glycogen, and proteins J Appl Physiol, January 1, 2004; 96(1): 32 - 40. [Abstract] [Full Text] [PDF]
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