title: Oxidative fuel selection and shivering thermogenesis during a 12- and 24-h cold-survival simulation.
abstract: Because the majority of cold exposure studies are constrained to short-term durations of several hours, the long-term metabolic demands of cold exposure, such as during survival situations, remain largely unknown. The present study provides the first estimates of thermogenic rate, oxidative fuel selection, and muscle recruitment during a 24-h cold-survival simulation. Using combined indirect calorimetry and electrophysiological and isotopic methods, changes in muscle glycogen, total carbohydrate, lipid, protein oxidation, muscle recruitment, and whole body thermogenic rate were determined in underfed and noncold-acclimatized men during a simulated accidental exposure to 7.5 °C for 12 to 24 h. In noncold-acclimatized healthy men, cold exposure induced a decrease of ∼0.8 °C in core temperature and a decrease of ∼6.1 °C in mean skin temperature (range, 5.4-6.9 °C). Results showed that total heat production increased by approximately 1.3- to 1.5-fold in the cold and remained constant throughout cold exposure. Interestingly, this constant rise in Ḣprod and shivering intensity was accompanied by a large modification in fuel selection that occurred between 6 and 12 h; total carbohydrate oxidation decreased by 2.4-fold, and lipid oxidation doubled progressively from baseline to 24 h. Clearly, such changes in fuel selection dramatically reduces the utilization of limited muscle glycogen reserves, thus extending the predicted time to muscle glycogen depletion to as much as 15 days rather than the previous estimates of approximately 30-40 h. Further research is needed to determine whether this would also be the case under different nutritional and/or colder conditions.
authors.affiliation: Faculty of Health Sciences, University of Ottawa, Ottawa, Ontario, Canada; fhaman@uottawa.ca.
authors.forename: François
authors.initials: F
authors.lastname: Haman
authors.affiliation: Faculty of Health Sciences, University of Ottawa, Ottawa, Ontario, Canada;
authors.forename: Olivier L
authors.initials: OL
authors.lastname: Mantha
authors.affiliation: Department of Kinesiology, Brock University, St. Catharines, Ontario, Canada;
authors.forename: Stephen S
authors.initials: SS
authors.lastname: Cheung
authors.affiliation: Defense Research and Development Canada, Québec City, Québec, Canada;
authors.forename: Michel B
authors.initials: MB
authors.lastname: DuCharme
authors.affiliation: Department of Kinesiology, Brock University, St. Catharines, Ontario, Canada; Falck Safety Services Canada, Dartmouth, Novia Scotia, Canada; School Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, Newfoundland, Canada.
authors.forename: Michael
authors.initials: M
authors.lastname: Taber
authors.affiliation: Centre hospitalier universitaire de Sherbrooke, Sherbrooke, Québec, Canada; and.
authors.forename: Denis P
authors.initials: DP
authors.lastname: Blondin
authors.affiliation: Department of Kinesiology, Brock University, St. Catharines, Ontario, Canada;
authors.forename: Gregory W
authors.initials: GW
authors.lastname: McGarr
authors.affiliation: Department of Kinesiology, Brock University, St. Catharines, Ontario, Canada;
authors.forename: Geoffrey L
authors.initials: GL
authors.lastname: Hartley
authors.affiliation: School Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, Newfoundland, Canada.
authors.forename: Zach
authors.initials: Z
authors.lastname: Hynes
authors.affiliation: School Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, Newfoundland, Canada.
authors.forename: Fabien A
authors.initials: FA
authors.lastname: Basset
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D001831:Body Temperature / Q000502:physiology; D001833:Body Temperature Regulation / Q000502:physiology; D003080:Cold Temperature; D004040:Dietary Carbohydrates / Q000378:metabolism; D004734:Energy Metabolism / Q000502:physiology; D006003:Glycogen / Q000378:metabolism; D006801:Humans; D050356:Lipid Metabolism / Q000502:physiology; D008055:Lipids / Q000502:physiology; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology; D010084:Oxidation-Reduction; D010101:Oxygen Consumption / Q000502:physiology; D012768:Shivering / Q000502:physiology*; D012881:Skin Temperature / Q000502:physiology; D022722:Thermogenesis / Q000502:physiology*; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D004040:Dietary Carbohydrates; D008055:Lipids; D006003:Glycogen
keywords: cold survival; energy needs; fuel selection; muscle recruitment