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Effects of carbohydrate availability on sustained shivering II. Relating muscle recruitment to fuel selection

¹Biology Department and ³School of Human Kinetics, University of Ottawa, Ottawa K1N 6N5; ²Defence R&D Canada, Ottawa K1A 0Z4; and ⁴Defence R&D Canada, Toronto, Ontario, Canada M3M 3B9

Submitted 29 April 2003 ; accepted in final form 31 July 2003

The purpose of this study was to quantify how shivering activity would be affected by large changes in fuel metabolism (see Haman F, Peronnet F, Kenny GP, Doucet E, Massicotte D, Lavoie C, and Weber J-M, J Appl Physiol 96: 000–000, 2004). 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, we quantified the effects of changes in fuel selection on the shivering activity of eight large muscles representing >90% of total shivering muscle mass. Contrary to expectation, drastic changes in fuel metabolism [carbohydrates 28 vs. 65% of total heat production (_prod), lipids 53 vs. 23% _prod, and proteins 19 vs. 12% _prod 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 bursts/min), 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 reveals 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 the same thermogenic rate by oxidizing widely different fuel mixtures within the same muscle fibers.

energy metabolism; electromyography; shivering thermogenesis; shivering pattern; muscle fiber recruitment; glycogen reserves

This article has been cited by other articles:

				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]

				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]

				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]

				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]

				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]

				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]