The effect of different intensities of exercise on the excretion of epinephrine and norepinephrine

Anticipation of a potentially stressful situation can alter the activity of the sympathetic nervous system. The purpose of this study was to measure the effect of three different intensities of exercise on epinephrine (E) and norepinephrine (NE) excretion when the work test order was randomly assigned and the subjects were not informed of the test order. Six subjects exercised at work loads which averaged 49%, 65%, and 82% Vo2max. Each subject showed an increased rate of NE excretion as the work load increased. The differences among work loads were significant (P less than 0.01). The E response was less consistent. Two subjects showed the greatest rate of excretion at the lowest work load, and one subject showed no increase above his pre-exercise resting value. While NE excretion was closely related to the work load, factors other than exercise appeared to exert considerable influence on the rate of E excretion during exercise.