Effects of Temperature and Water Immersion on Plasma Catecholamines and Circulation*

Abstract

The effects of environmental air temperature of 6°C and 26°C on catecholamines (CA) and circulation were studied in eight male subjects during rest and during bicycle exercise at Wobla for45 min each. We found that resting at 6°C increased the norepinephrine (NE) levels to the same levels as endurance exercises at 6°C. The increase of CA levels was 2.5 to 3 times higher during work at 26°C compared with 6°C. During both rest and exercise at 6°C we found a higher stroke volume of the heart and a reduced heart rate (HR) with no or only small effects on the oxygen uptake and blood lactate levels compared with 26°C. Measurements of the skin temperatures showed large differences both at rest and during work; those of core temperature showed no changes at rest and a slightly more pronounced increase during work at 26°C compared with 6°C. The behavior of CA, plasma renin activity (PRA), plasma aldosterone (PA), and circulation were studied in 13 top class swimmers and 12 recreational swimmers during immersion into water of 27°C for 10 min. The recreational swimmers were additionally immersed into water of 21°C and 33°C. Even immersion at 33°C induced a small but significant increase of NE levels and of blood pressure (BP) values with no effect on the HR and blood lactate values. Epinephrine (EPI) showed a tendency to decrease. In water of 27°C and 21°C a further augmentation of NE values was found inversely to water temperature, and BP values were higher at 21°C than at 33°C. In connection with muscle shivering, at 21°C an additional elevation of blood lactate, HR, and EPI values could be observed. The increase of BP and unchanged HR was reproducible in water of 27°C in the trained swimmers, but the augmentation of CA levels seemed to be somewhat lower than that of the untrained. In summary, we could show that cold strain in resting people increases NE levels both on land and in water. The effect seems to be mediated by thermoreceptors of the skin and has hemo-dynamic effects with increased stroke volume of the heart and reduced blood flow to the skin. In water this thermoregulatory effect might cause a hyperdynamic circulation with increased preload and afterload of the heart. Glycolytic effects of NE were only observed in connection with muscle shivering. During exercise a higher environmental temperature enhances the augmentation of both CA. This may be caused by worse heat dissipation with an increase of core temperature and a larger blood flow to the body surface. Thereby, a higher sympathetic tone might be needed to insure adequate perfusion of working muscles by vasoconstriction in other areas of the circulatory system.

Key words

plasma catecholamines - circulation - water immersion - thermoregulation - plasma renin activity - plasma aldosterone