CHANGE IN SYMPATHETIC ACTIVITY, CARDIOVASCULAR FUNCTIONS AND PLASMA-HORMONE CONCENTRATIONS DUE TO COLD-WATER IMMERSION IN MEN

The purpose of this study was to determine whether or not repeated sho rt-term cold water immersions can induce a change in the activity of t he sympathetic nervous system and, consequently, in cardiovascular fun ctions in healthy young athletes, Changes in some plasma hormone conce ntrations were also followed. A single cold water immersion (head-out, al 14 degrees C, for 1 h) increased sympathetic nervous system activi ty, as evidenced by a four-fold increase (P <0.05) in plasma noradrena line concentration. Plasma adrenaline and dopamine concentrations were not increased significantly. Plasma renin-angiotensin activity was re duced by half (P <0.05) during immersion but plasma aldosterone concen tration was unchanged. Stimulation of the sympathetic nervous system d uring immersion did not induce significant changes in heart rate: but induced peripheral vasoconstriction (as judged from a decrease in skin temperature) and a small increase (by 10%) in systolic and diastolic blood pressures. No clear change in reactivity of the sympathetic nerv ous system was observed due 10 repealed cold water immersions (three t imes a week, for 6 weeks). Neither the plasma renin-angiotensin activi ty, aldosterone concentration nor cardiovascular parameters were signi ficantly influenced by repealed cold water immersions. A lowered diast olic pressure and an increase in peripheral vasoconstriction were obse rved after cold acclimation. however. Evidently, the repeated cold sti muli were not sufficient to induce significant adaptational changes in sympathetic activity and hormone production.