1. The effects of leg muscle pumping (tiptoeing) and tensing (leg-crossing) on orthostatic blood pressure were investigated in six healthy adult subjects (aged 28-34 years) and in seven patients with severe hypo-adrenergic orthostatic hypotension (aged 20-65 years). 2. Finger arterial pressure was monitored. Relative changes in left ventricular stroke volume were computed by a pulse contour method. 3. Tiptoeing increased mean arterial pressure (7 +/- 5 mmHg) in the healthy subjects, but not in the patients, whereas cardiac output increased in both groups, although by more in the healthy adults than in the patients (35 +/- 10% versus 20 +/- 11%, P < 0.05). Systemic vascular resistance decreased substantially in both groups while tiptoeing. Leg-crossing did not affect arterial pressure in the healthy subjects, although stroke volume had increased. In contrast, in the patients an increase in cardiac output (16 +/- 12%) and mean blood pressure (13 +/- 13 mmHg) was observed. 4. Tiptoeing and leg-crossing have different effects on orthostatic blood pressure in healthy adult subjects and in patients with autonomic failure. In normal humans, tiptoeing increases arterial pressure, whereas leg-crossing has little effect. In the patients, in contrast, tiptoeing has little effect, whereas leg-crossing increases arterial pressure considerably. Patients with autonomic failure should be instructed to apply leg-crossing to combat orthostatic dizziness.
