title: Effects of reduced ambient temperature on fat utilization during submaximal exercise.
abstract: OBJECTIVE
  The influence of cold air exposure on fuel utilization during prolonged cycle exercise was investigated.
  
  
  METHODS
  Nine male subjects cycled for 90 min in ambient temperatures of -10 degrees C, 0 degrees C, 10 degrees C, and 20 degrees C. External work performed between conditions was constant. Mean oxygen consumption (VO2) over the 90 min in the 20 degrees C trial corresponded to 64 +/- 5.8% VO2peak.
  
  
  RESULTS
  Although mean skin temperature was different between trials (P < 0.05), rectal temperatures were not different. At -10 degrees C and 0 degrees C, the respiratory exchange ratio was higher compared with 10 degrees C and 20 degrees C (0.98 +/- 0.01 and 0.97 +/- 0.01 vs 0.92 +/- 0.01 and 0.91 +/- 0.01; P < 0.05). The associated rates of fat oxidation were lower at -10 degrees C and 0 degrees C compared with 10 degrees C and 20 degrees C (0.15 +/- 0.06 and 0.17 +/- 0.06 vs 0.35 +/- 0.06 and 0.40 +/- 0.04 g.min-1; P < 0.05). Blood glycerol was lower at -10 degrees C and 0 degrees C compared with 20 degrees C (P < 0.05); mean values were 0.13 +/- 0.0, 0.13 +/- 0.0, and 0.18 +/- 0.0 mmol.L-1 for the -10 degrees C, 0 degrees C, and 20 degrees C trials, respectively. Mean VO2 was lower in the -10 degrees C trial than the 20 degrees C trial (2.53 +/- 0.06 vs 2.77 +/- 0.09. L.min-1; P < 0.05). Mean blood glucose concentrations were lower at -10 degrees C than 20 degrees C (4.9 +/- 0.2 vs 5.3 +/- 0.1 mmol.L-1; P < 0.05). Although plasma epinephrine concentrations were greater during the 20 degrees C trial compared with all other trials (P < 0.05), plasma norepinephrine did not differ between trials.
  
  
  CONCLUSIONS
  The diminished fat oxidation at colder temperatures potentially reflects a reduction in lipolysis and/or mobilization of FFA or impairment in the oxidative capacity of the muscle.
authors: Strathclyde Institute for Biomedical Sciences, University of Strathclyde, Glasgow, UK. j.layden@ucc.ac.uk
authors: Joseph D
authors: JD
authors: Layden
authors: Mark J
authors: MJ
authors: Patterson
authors: Myra A
authors: MA
authors: Nimmo
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism*; D000328:Adult; D015308:Anaerobic Threshold / Q000502:physiology; D000704:Analysis of Variance; D001642:Bicycling; D001831:Body Temperature; D003081:Cold Climate; D004734:Energy Metabolism; D015444:Exercise / Q000502:physiology*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D006339:Heart Rate; D006801:Humans; D050356:Lipid Metabolism; D008055:Lipids / Q000097:blood; D008297:Male; D011659:Pulmonary Gas Exchange; D013997:Time Factors
chemical_list: D005230:Fatty Acids, Nonesterified; D008055:Lipids