Related Experiment Video
Updated: Aug 18, 2026

Tilt Testing with Combined Lower Body Negative Pressure: a "Gold Standard" for Measuring Orthostatic Tolerance
Published on: March 21, 2013
Leg vascular resistance increases during head-up tilt in paraplegics
Jan T Groothuis1, Cécile R L Boot, Sibrand Houtman
1Department of Physiology, University Medical Centre Nijmegen, The Netherlands.
Abstract:
Despite loss of centrally mediated sympathetic vasoconstriction to the legs, spinal cord-injured individuals cope surprisingly well with an orthostatic challenge. This study assessed changes in leg vascular resistance following head-up tilt in healthy (C) and in paraplegic (P) individuals. After 10 min of supine rest, subjects were tilted 30 degrees head-up. Mean arterial pressure (MAP) and total peripheral resistance (TPR) increased in C (MAP from 76.7 +/ -6.6 mmHg to 80.6 +/- 8.2 mmHg; TPR from 1.12 +/- 0.26 AU to 1.19 +/ -0.31 AU) while both remained unchanged in P. Echo Doppler ultrasound determined red blood cell velocity in the femoral artery, which decreased (P from 18.9+/-6.2 cm/s to 12.5 +/- 4.5 cm/s, P = 0.001; C from 16.3 +/- 6.2 cm/s to 10.8 +/- 5.0 cm/s, P = 0.001) and leg vascular resistance, which increased (P from 402 +/- 137 AU to 643 +/- 274 AU, P = 0.001; C from 238 +/- 68 AU to 400 +/- 122 AU, P = 0.003) from supine to upright. The present study shows that independent of supraspinal sympathetic control, humans are able to increase leg vascular resistance and maintain blood pressure during head-up tilt.
More Related Videos
Related Concept Videos
Vascular Resistance
The primary determinants of vascular resistance are vessel diameter, blood viscosity, and vessel length. Among these, vessel diameter plays the most significant role due to the fourth power relationship described by...
Increased Intracranial Pressure l: Introduction
Increased Intracranial Pressure ll: Pathophysiology
Venous Return
What is Venous Return?
Venous return refers to the rate at which blood flows back to the heart from the body's peripheral veins. It's an integral part of the circulatory system as it...

