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The nature of the exercise stimulus
Acta Physiologica Scandinavica. Supplementum
|January 1, 1986
Summary
The muscle chemoreflex, triggered by metabolic byproducts in exercising muscles, plays a significant role in cardiovascular regulation. Its sensitivity varies with exercise intensity, becoming more prominent during heavier exertion.
Area of Science:
- Exercise Physiology
- Cardiovascular Regulation
- Neuroscience
Background:
- Two main hypotheses explain exercise's cardiovascular control: Central Command and Muscle Chemoreflex.
- The Muscle Chemoreflex involves skeletal muscle chemosensors detecting metabolic byproducts.
- This reflex is known to trigger pressor responses in ischemic muscle.
Purpose of the Study:
- To assess the physiological importance of the muscle chemoreflex during exercise.
- To investigate the relationship between exercise intensity, muscle blood flow, and pressor responses.
Main Methods:
- Stepwise partial occlusions of the terminal aorta were performed in exercising dogs.
- Arterial pressure and terminal aortic flow were monitored.
- Femoral venous concentrations of lactate and potassium, and PO2 were measured.
Main Results:
- The pressor response magnitude correlated with reductions in aortic flow and pressure.
- Muscle chemoreflex sensitivity was low with a threshold in mild exercise.
- In heavier exercise, sensitivity was high, suggesting a tonic role.
Conclusions:
- The muscle chemoreflex contributes to cardiovascular control during exercise, particularly at higher intensities.
- Lactate accumulation appears to be a key metabolic signal for this reflex.
- Further research is needed to identify the precise metabolic signal.