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Conducting Maximal and Submaximal Endurance Exercise Testing to Measure Physiological and Biological Responses to Acute Exercise in Humans
Published on: October 17, 2018
Theoretical analysis of the noncardiac limits to maximum exercise
1Royal Victoria Hospital, Critical Care Division, McGill University, 687 Pine Avenue West, Montréal, QC H3A 1A1, Canada. sheldon.magder@muhc.mcgill.ca
Canadian Journal of Physiology and Pharmacology
|November 27, 2002
Summary
During exercise, significant shifts in blood flow distribution and venous return are crucial for maximizing cardiac output, especially when right atrial pressure is low or constant. Muscle contractions help manage venous pressure and prevent plasma leakage.
Area of Science:
- Cardiovascular Physiology
- Exercise Physiology
Background:
- Cardiac output is influenced by cardiac function and venous return.
- Right atrial pressure (Pra) significantly impacts the determinants of cardiac output.
Purpose of the Study:
- To analyze the necessary changes in venous return function for maximal cardiac output during exercise when Pra is zero or constant.
- To expand existing circulation models to include circuit parameters like venous resistance, capacitance, and muscle contractions.
Main Methods:
- Utilized a model of the systemic circulation with two parallel compliant regions.
- Incorporated effects of changes in venous resistance, capacitance, and muscle contractions.
- Normalized data from animal studies to a 70-kg human model.
Main Results:
- Achieving high cardiac output during peak exercise requires substantial alterations in blood flow distribution.
- Recruitment of unstressed vascular volume and changes in venous resistance are critical.
- Increased peripheral flow leads to elevated venous pressure in working muscles.
Conclusions:
- Marked changes in blood flow distribution, unstressed volume recruitment, and venous resistance are essential for peak exercise cardiac output.
- Muscle contractions play a key role in transiently reducing venous pressure, preventing excessive plasma filtration during exercise.
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