Figure 2.

Original record of arterial pressure during supine and head down tilt leg exercise in a 44-year-old male who had undergone thoracolumbar sympathectomy for the treatment of severe hypertension. The patient had normal autonomic innervation of the heart and could increase his heart rate and cardiac output. Thus, the fall in blood pressure during exercise seen in this figure is some of the first evidence that the sympathetic nerves must restrain blood flow to active muscles to regulate arterial pressure during exercise. Note that even the head down position used to maximize cardiac filling does not prevent the fall in arterial pressure during exercise. Figure from Marshall et al. (1961b).