Related Experiment Videos
Upright posture reduces forearm blood flow early in exercise
J K Shoemaker1, P M McQuillan, L I Sinoway
1Section of Cardiology, The Pennsylvania State University College of Medicine, The Milton S. Hershey Medical Center, Hershey, Pennsylvania 17033, USA. kshoemak@gcrc.hmc.psghs.edu
The American Journal of Physiology
|May 8, 1999
Summary
Upright posture reduces forearm blood flow (FBF) during early exercise. This reduction is mainly due to lower venous pressure, not sympathetic vasoconstriction, impacting exercise hyperemia.
Area of Science:
- Physiology
- Exercise Physiology
- Cardiovascular Regulation
Background:
- Upright posture influences cardiovascular responses, including blood flow dynamics.
- Understanding how posture affects exercise-induced hyperemia is crucial for exercise physiology.
Purpose of the Study:
- To test the hypothesis that upright posture modulates forearm blood flow (FBF) early in exercise.
- To investigate the roles of venous pressure and sympathetic activity in posture-induced changes in FBF.
Main Methods:
- Six subjects performed single and repeated handgrip contractions in supine and 70° head-up tilt (HUT) positions.
- Forearm blood flow (FBF), brachial artery mean blood velocity (MBV), and mean arterial pressure (MAP) were measured.
- Venous pressure (Pv) was manipulated by arm position, and sympathetic activity was altered via blockade.
Main Results:
- Head-up tilt (HUT) reduced antecubital venous pressure (Pv) compared to the supine position.
- Both single and repeated contractions showed reduced FBF and vascular conductance in HUT.
- Sympathetic blockade augmented FBF but did not alter the effect of HUT on postcontraction hyperemia.
Conclusions:
- Upright posture diminishes the early exercise hyperemic response.
- Reduced venous pressure, not sympathetic vasoconstriction, is the primary factor for attenuated FBF in HUT.
- Venous pressure significantly influences exercise-induced hyperemia, particularly in upright postures.
Keywords:
Non-programmatic