Effects of Caffeine on the Metabolic and Catecholamine Responses to Exercise in 5 and 28 Degrees C

Med Sci Sports Exerc. 1994 Apr;26(4):453-8.

Abstract

The influence of caffeine on the metabolic and catecholamine responses to mild exercise in a cold and a warm environment was studied in eight healthy males. The subjects performed 60 min of cycling at 50% VO2max in a cold environment (5 degrees C and 70% relative humidity) and a warm environment (28 degrees C and 50% relative humidity) 30 min after ingesting caffeine (5 mg.kg-1 body weight) or placebo (dextrose). Caffeine ingestion prior to exercise in the warm environment resulted in increased plasma epinephrine, with no effect on plasma norepinephrine. Neither lipid nor carbohydrate metabolism was altered by caffeine in the warm trial. Exercise in the cold environment (placebo) produced increased VO2 and carbohydrate metabolism, decreased lipid metabolism, and no difference in plasma catecholamines compared with the warm-placebo trial. Responses to the combination of caffeine ingestion and the cold environment did not differ from cold-placebo responses in VO2 during the cycling bout. However, in the cold-caffeine trial plasma epinephrine was elevated. In addition, fat oxidation and serum free fatty acids were elevated in the cold-caffeine condition. Carbohydrate oxidation was depressed, while serum glucose and blood lactate were elevated in this trial compared to cold-placebo. Thus, caffeine increases plasma epinephrine; cold increases oxygen consumption and carbohydrate metabolism, while decreasing lipid metabolism; and the combination of caffeine and cold during exercise increases plasma epinephrine and lipid metabolism, but decreases carbohydrate metabolism.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Blood Glucose / analysis
  • Body Temperature / physiology
  • Caffeine / blood
  • Caffeine / pharmacology*
  • Carbohydrate Metabolism*
  • Carbon Dioxide / analysis
  • Cold Temperature*
  • Double-Blind Method
  • Epinephrine / blood*
  • Exercise Test
  • Fatty Acids, Nonesterified / blood
  • Heart Rate / drug effects
  • Heart Rate / physiology
  • Hot Temperature*
  • Humans
  • Lactates / blood
  • Lipid Metabolism*
  • Male
  • Norepinephrine / blood*
  • Oxidation-Reduction / drug effects
  • Oxygen Consumption / drug effects
  • Oxygen Consumption / physiology
  • Physical Exertion / physiology*
  • Placebos
  • Pulmonary Gas Exchange / drug effects
  • Pulmonary Gas Exchange / physiology

Substances

  • Blood Glucose
  • Fatty Acids, Nonesterified
  • Lactates
  • Placebos
  • Carbon Dioxide
  • Caffeine
  • Norepinephrine
  • Epinephrine