Substrate utilization in leg muscle of men after heat acclimation

J Appl Physiol (1985). 1987 Jul;63(1):31-5. doi: 10.1152/jappl.1987.63.1.31.

Abstract

Eight men were heat acclimated (39.6 degrees C and 29.2% rh) for 8 days to examine changes in substrate utilization. A heat exercise test (HET), (cycling for 60 min; 50% maximal O2 consumption) was performed before (UN-HET) and after (ACC-HET) the acclimation period. Muscle glycogen utilization (67.0 vs. 37.6 mmol/kg wet wt), respiratory exchange ratio (0.85 +/- 0.002 vs. 0.83 +/- 0.001), and calculated rate of carbohydrate oxidation (75.15 +/- 1.38 vs. 64.80 +/- 1.52 g/h) were significantly reduced (P less than 0.05) during the ACC-HET. Significantly lower (P less than 0.05) femoral venous glucose (15, 30, and 45 min) and lactate (15 min) levels were observed during the ACC-HET. No differences were observed in plasma free fatty acid (FFA) and glycerol concentrations or glucose, lactate and glycerol arteriovenous uptake/release between tests. A small but significant increase (P less than 0.05) above resting levels in FFA uptake was observed during the ACC-HET. Leg blood flow was slightly greater (P greater than 0.05) during the ACC-HET (4.64 +/- 0.13 vs. 4.80 +/- 0.13 l/min). These findings indicate a reduced use of muscle glycogen following heat acclimation. However, the decrease is not completely explained by a shift toward greater lipid oxidation or increased blood flow.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Acclimatization*
  • Adult
  • Carbohydrate Metabolism
  • Fatty Acids, Nonesterified / blood
  • Glycerol / blood
  • Glycogen / metabolism
  • Hot Temperature
  • Humans
  • Leg
  • Male
  • Muscles / blood supply
  • Muscles / metabolism*
  • Oxygen Consumption
  • Physical Exertion*
  • Regional Blood Flow

Substances

  • Fatty Acids, Nonesterified
  • Glycogen
  • Glycerol