Does limb angular motion raise limb arterial pressure?

Abstract

Aim: Mechanical factors such as the muscle pump have been proposed to augment flow by several mechanisms. The potential for limb angular motion to augment local perfusion pressure (pressure = 1/2ρr2ω 2, where ρ is the fluid density, r the radius and ω the angular velocity) has been overlooked. We sought to test the hypothesis that limb angular motion augments limb arterial pressure. Methods: Nine human subjects performed horizontal shoulder flexion (∼±90° at 0.75 Hz for 30 s). We measured finger arterial pressure (photoplethysmography) in the moving (Trial 1) and non-moving arm (Trial 2) in separate trials along with the pressure (strain gauge) generated at the fingers within a length of water-filled tubing mounted on the moving arm in both trials. Results: Arm swinging raised (P < 0.05) the mean pressure measured in the tubing by 11 ± 2 and 14 ± 2 mmHg (Trials 1 and 2 respectively). In response to exercise, the rise in mean finger arterial pressure in the swinging limb (18 ± 3 mmHg, Trial 1) exceeded (P < 0.05) the rise in the resting limb (8 ± 2 mmHg, Trial 2) by an amount similar to the 11 mmHg rise in pressure generated in the tubing in Trial 1. Conclusions: We conclude that the swinging of a limb creates centrifugal force (a biomechanical centrifuge) which imparts additional pressure to the arteries, but not the veins owing to the venous valves, which further widens the arterial-venous pressure difference. © 2008 The Authors.