Related Experiment Videos
Exercise O2 transport model assuming zero cytochrome PO2 at VO2 max
1Cardiovascular Research Institute, San Francisco, California 94143.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|August 1, 1994
Summary
This study models maximal oxygen consumption (VO2max) using a zero surface PO2 hypothesis for cytochrome aa3. The model reveals the Bohr effect enhances VO2max and influences oxygen extraction during intense exercise.
Area of Science:
- Exercise Physiology
- Biophysics
Background:
- Cytochrome aa3 acts as a polarographic cathode, capturing oxygen at -0.6 V.
- Maximal oxygen consumption (VO2max) is linked to eliminating oxygen backpressure, achieving zero surface PO2.
Purpose of the Study:
- To model the relationship between oxygen consumption and PO2 levels in muscle.
- To investigate the role of the Bohr effect and lactate accumulation in exercise limitation.
Main Methods:
- Developed a model incorporating oxygen consumption, muscle venous PO2, myoglobin, and cytochrome PO2.
- Utilized published data on leg venous PO2, pH, and blood lactate during exercise.
- Modeled oxygen dissociation curves for hemoglobin and myoglobin, including the Bohr effect.
Main Results:
- Myoglobin must be 90% down the oxygen gradient to extract 75% of O2 at VO2max.
- The Bohr effect increases VO2max by 15-30% and stabilizes venous PO2 at high work rates.
- Rising lactate may shift energy balance towards aerobic metabolism during heavy work.
Conclusions:
- The zero surface PO2 hypothesis provides a framework for understanding VO2max limitations.
- The Bohr effect plays a significant role in enhancing maximal oxygen consumption.
- Metabolic shifts, influenced by lactate, are critical in heavy exercise physiology.