Influence of cold, exercise, and caffeine on catecholamines and metabolism in men

Abstract

Recently we found that caffeine ingestion did not enhance either thermal or fat metabolic responses to resting in cold air, despite an increase in plasma epinephrine and free fatty acids. Theophylline, another methylxanthine, has been shown to be effective during exercise but not at rest during cold stress. Therefore we hypothesized that caffeine ingestion before exercise in cold air would have a thermal-metabolic impact by increasing fat metabolism and increasing oxygen consumption. Young adult men (n = 6) who did not normally have caffeine in their diet performed four double-blind trials. Thirty minutes after ingesting placebo (dextrose, 5 mg/kg) or caffeine (5 mg/kg) they either exercised (60 W) or rested for 2 h in 5 degrees C air. Cold increased (P less than 0.05) plasma norepinephrine while both caffeine and exercise increased (P less than 0.05) epinephrine. Serum free fatty acids and glycerol were increased, but there were no differences between rest and exercise or placebo and caffeine. Caffeine had no influence on either respiratory exchange ratio or oxygen consumption either at rest or during exercise. The exercise trials did not significantly warm the body, and they resulted in higher plasma norepinephrine concentrations and lower mean skin temperatures for the first 30 min. The data suggest that skin temperature stimulates plasma norepinephrine while caffeine has little effect. In contrast, caffeine and exercise stimulate plasma epinephrine while cold has minimal effect. Within the limits of this study caffeine gave no thermal or metabolic advantage during a cold stress.

Study of Active Substances Involved in Skin Dysfunction Induced by Crowding Stress. I. Effect of Crowding and Isolation on Some Physiological Variables, Skin Function and Skin Blood Perfusion in Hairless Mice.

“…This suggests that isolation mainly activates the sympathetic nervous system, as seen in animals exposed to cold stress. 41) These findings demonstrate that crowding is more common as a stressor than social isolation, as the former induced most of the changes reported previously in experimental stress models. 11,[34][35][36][37][38][39] As noted above, there are apparent differences in physiological variables between crowded and isolated animals.…”

Metabolic effects of caffeine ingestion and physical work in 75‐year old citizens. A randomized, double‐blind, placebo‐controlled, cross‐over study

“…In young healthy adults, the metabolic changes following caffeine ingestion and physical work are well described. Caffeine ingestion increases the plasma concentration of epinephrine both at rest 1–3 and during exercise, 1,4–7 whereas the plasma concentration of norepinephrine is unaffected in most studies 1,6–8 Caffeine also increases the plasma concentration of free fatty acids (FFA), 3,8–15 glycerol, 1–3 glucose, 11–13,16–18 insulin 2,18 and lactate 3,11–13,16–18 during exercise in some, but not all 1,8,10,19–22 studies. One study compared the metabolic effects of caffeine ingestion in younger men and elderly men and found that older men showed a smaller increase in fatty acid availability after caffeine ingestion without any relation to alterations in norepinephrine kinetics or fat oxidation 23 …”

The Ability of Perindopril of Modulate Behavioural,Neuroendocrinal and Testicular Profiles in Stressed Rats

“…attempt suppressed in comparison to control. to be consumed in enhancing thermal metabolic reactions to restore basal metabolic rate to prestressor level, rather than being consumed in heightening any aggressive attemptl22, 26,27].…”