Sexual activity in the missionary position, as a form of physical exercise, may be slightly more vigorous for the man than in other positions. A study conducted by Bohlen et al. found that "man-on-top coitus required more metabolic expenditure than woman-on-top coitus" and that the heart rate during man-on-top sex was higher than in self-stimulation, partner stimulation, or woman-on-top. In contrast, one study showed that there was no difference in heart rate or blood pressure when comparing these two basic positions, while another showed only a minor decrease in oxygen consumption or exertion with the 'man-on-bottom' technique during orgasm.