Related Experiment Videos
Evidence for tissue diffusion limitation of VO2max in normal humans
1Department of Medicine, University of California, San Diego, La Jolla 92093.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|July 1, 1989
Summary
This study investigated oxygen transport during maximal exercise, finding that reduced oxygen levels limit maximal oxygen consumption (VO2max). Measurements of muscle and venous blood oxygen levels correlated linearly with VO2max, supporting a tissue diffusion limitation hypothesis.
Area of Science:
- Exercise Physiology
- Human Physiology
- Cardiovascular Physiology
Background:
- Previous research suggested tissue diffusion limitation of VO2max at 90% maximal oxygen consumption (VO2max).
- Further investigation was needed to confirm this limitation at VO2max and examine muscle blood oxygen directly.
Purpose of the Study:
- To extend prior observations to VO2max.
- To directly examine effluent venous blood from muscle during exercise at VO2max.
- To test the hypothesis of tissue diffusion limitation of VO2max.
Main Methods:
- Six healthy men performed maximal cycling tests breathing air, 15% O2, and 12% O2.
- Blood samples were taken from femoral vein, mixed venous, and radial artery to measure PO2, PCO2, pH, and lactate.
- Oxygen consumption (VO2) and CO2 production (VCO2) were measured via expired gas analysis.
Main Results:
- VO2max decreased significantly with reduced inspired oxygen (air: 61.5, 15% O2: 48.6, 12% O2: 38.1 ml.kg-1.min-1).
- Femoral venous PO2 (PfVO2), mixed venous PO2 (PVO2), and calculated muscle capillary PO2 (PmCO2) all decreased linearly with VO2max.
- All PO2 variables showed a strong linear relationship with VO2max (r=0.99) with an intercept near the origin.
Conclusions:
- Tissue diffusion limitation of VO2max may be present in normal humans.
- The linear relationship between PVO2, PfVO2, PmCO2, and VO2max suggests these measures can be used to evaluate the diffusion limitation hypothesis.