Cardiac Rhythm and Urinary Excretion of Catecholamine under Mental Work and Physical Exercise

Abstract

In six normal adults changes of cardiac rhythm and urinary excretion of catecholamine were studied under mental work and physical exercise. The mental tests consisted of continuous mental calculations, and the physical tests involved the active extension and contraction of legs. Cardiac rhythm during the tests was recorded continuously by means of Matsuda's cardiotachograph. In both mental and physical loads, the heart rate distinctly increased without exception, and a close relationship was observed between the strength of load and the maximum heart rate. Catecholamine levels in urine were measured before and after the mental calculations and walking, and those values were compared with each other. In the mental tests, the excretion of adrenaline was higher than that of noradrenaline, with average rate of 2.19 for adrenaline and 1.22 for noradrenaline. The increased output of adrenaline and noradrenaline in urine was also observed in the physical exercises. However, the increase in adrenaline was smaller than that of noradrenaline, that is, the average rate of adrenaline was 1.88, while that of noradrenaline was 2.25. From these findings, conclusion may be made that the mental reaction causes the release of adrenaline from the adrenal medullae, whereas physical exercise causes discharge of noradrenaline from the sympathetic nerve endings.