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Vasodilation and muscle pump contribution to immediate exercise hyperemia
M E Tschakovsky1, J K Shoemaker, R L Hughson
1Department of Kinesiology, University of Waterloo, Ontario, Canada.
The American Journal of Physiology
|October 1, 1996
Summary
The muscle pump aids forearm blood flow, but rapid vasodilation also contributes to exercise hyperemia. This study investigated the mechanisms behind rapid increases in skeletal muscle blood flow during exercise.
Area of Science:
- Physiology
- Exercise Physiology
- Cardiovascular Physiology
Background:
- Rapid increases in skeletal muscle blood flow (exercise hyperemia) occur within seconds of muscle contraction.
- The exact mechanisms driving this rapid hyperemia, particularly the role of the muscle pump versus vasodilation, remain debated.
Purpose of the Study:
- To investigate the contribution of the mechanical muscle pump effect to rapid exercise hyperemia.
- To differentiate the effects of venous emptying from active vasodilation in increasing forearm blood flow.
Main Methods:
- Forearm blood flow was measured in humans with the arm positioned above or below heart level.
- Simulated rhythmic muscle pump function using cuff inflation/deflation.
- Measured blood flow during single voluntary muscle contractions and contractions within cuff inflations.
Main Results:
- Rhythmic cuff inflation (simulating muscle pump) increased blood flow when the arm was below heart level, but not above.
- Blood flow following single muscle contractions was significantly higher than following simulated venous emptying within 2 seconds.
- The mechanical muscle pump effect accounted for 46-60% of the peak blood flow increase during contraction, depending on arm position.
Conclusions:
- A functional muscle pump exists in the human forearm.
- Rapid vasodilation, detectable within 2 seconds, also significantly contributes to early exercise hyperemia alongside the muscle pump.