Cardiac output response to standing and treadmill walking

Cardiac output measurements during cardiac catheterization were obtained in normal subjects for several grades of treadmill exercise. Femoral venous blood was sampled and the A-V oxygen difference for the exercising leg obtained. Measurements of central and femoral A-V oxygen difference and total oxygen uptake were also obtained in normal subjects during supine rest and during standing. When subjects merely stood, the A-V oxygen difference for the leg increased (whether the leg bore weight or not) much more than did that for the whole body. During treadmill walking femoral A-V oxygen difference was usually no greater than that during standing. Cardiac output was smaller and total body A-V oxygen difference was greater for treadmill walking than for supine bicycle exercise in which comparable levels of oxygen uptake were achieved. It is clear that change in posture alters the cardiac output response to exercise. An important aspect of the altered response was a marked difference in the circulation within the leg for these two postures both at rest and during exercise. Submitted on August 8, 1960