Effect of physical exercise on plasma melatonin levels in normal volunteers

Abstract

Plasma melatonin, cortisol and prolactin levels were determined in clinically normal adult Black male volunteers before, immediately after, and 1 hour after a period of controlled physical exercise. In all subjects the levels of these three hormones showed highly significant increases immediately after exercise and returned to pre-exercise levels 1 hour after physical exertion. In subjects who exercised in a room with reduced environmental lighting (54 lux), the plasma melatonin level immediately after exercise was significantly higher than in the group who exercised in a room with a lighting level of 320 lux. Reduction of environmental lighting had no effect on the plasma cortisol and prolactin values immediately after exercise. Significant positive relationships between post-exercise melatonin levels and body mass, age and pulse rate were noted in all volunteers. Since plasma melatonin reached a plateau level after 30 minutes, it is suggested that controlled exercise (step-climbing), which induces an energy output of 185 W/m2 body surface, conducted in a room with reduced environmental lighting for a period of 30 minutes, may form the basis for a pineal function test.