The endorphin response of women to sleep loss and exercise.

The purpose of this investigation was to examine the combined effect of sleep loss and exercise on plasma beta-endorphin levels. Seven healthy women completed a 1-h run at approximately 80% VO2 max on a motorized treadmill after a normal night's sleep and again after 36 h of sleep deprivation. Venous blood samples were obtained before and immediately after each run. Oxygen uptake, heart rate, blood pressure, and ratings of perceived exertion were obtained during each trial. Resting beta-endorphin levels were 4.5 +/- 0.2 pmol.L-1 for the control trial and 4.7 +/- 0.7 pmol.L-1 for the sleep deprived trials. Exercise after normal sleep resulted in an average endorphin level of 19.4 +/- 6.8 pmol.L-1. Sleep loss did not significantly alter the post-exercise beta-endorphin response, averaging 19.4 +/- 8.7 pmol.L-1. Both trials resulted in similar oxygen uptake (41.8 +/- 2.3 ml.kg-1.min-1), heart rate (163 +/- 4 beats.min-1), mean blood pressure (98 +/- 3 mm Hg), and rating of perceived exertion (12.0 +/- 0.2). These results suggest that 36 h of sleep deprivation does not impose sufficient stress to alter the resting endorphin response, nor does it affect the endorphin response to high-intensity exercise.