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Exercise stroke volume relative to plasma-volume expansion.
M K Hopper1, A R Coggan, E F Coyle
1Department of Physical and Health Education, University of Texas at Austin 78712.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|January 1, 1988
Summary
Plasma-volume expansion significantly increases stroke volume in untrained men during exercise. Endurance-trained individuals with naturally higher blood volume show no further stroke volume increase with expansion.
Area of Science:
- Exercise Physiology
- Cardiovascular Physiology
Background:
- Stroke volume (SV) during exercise is influenced by plasma volume (PV).
- Untrained individuals may have suboptimal blood volume (BV) compared to endurance-trained athletes.
Purpose of the Study:
- To determine the effects of plasma-volume expansion on stroke volume during submaximal exercise.
- To compare the response in untrained versus endurance-trained men.
Main Methods:
- Intravenous infusion of dextran solution to expand plasma volume in untrained males.
- CO2 rebreathing technique to measure stroke volume during submaximal exercise in upright and supine positions.
- Comparison with naturally plasma-volume expanded endurance-trained males.
Main Results:
- Plasma-volume expansion (approx. 400 ml) increased stroke volume by 11% in untrained men.
- Further plasma-volume expansion did not yield additional stroke volume increases.
- Endurance-trained men, with naturally higher blood volume, did not show increased stroke volume after PV expansion.
- When blood volume was matched, untrained men exhibited higher stroke volume and lower peripheral resistance compared to trained individuals.
Conclusions:
- Exercise stroke volume in untrained men is preload-dependent and responsive to initial plasma-volume expansion.
- Suboptimal blood volume contributes significantly to the lower exercise stroke volume observed in untrained compared to endurance-trained men.