Related Experiment Videos
Muscle metaboreflex increases ventricular performance in conscious dogs
1Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.
The American Journal of Physiology
|August 5, 1998
Summary
The muscle metaboreflex increases cardiac output by enhancing ventricular contractility, sustaining stroke volume despite increased heart rate. This response helps maintain systemic arterial pressure during exercise.
Area of Science:
- Cardiovascular Physiology
- Exercise Physiology
- Autonomic Nervous System
Background:
- Skeletal muscle ischemia triggers the muscle metaboreflex, a neural reflex.
- This reflex increases systemic arterial pressure, heart rate, and cardiac output.
- The effect of the muscle metaboreflex on ventricular performance is not fully understood.
Purpose of the Study:
- To investigate if muscle metaboreflex activation increases ventricular performance.
- To determine the role of ventricular contractility in sustaining cardiac output during reflex activation.
Main Methods:
- Utilized conscious, instrumented dogs performing treadmill exercise.
- Activated the muscle metaboreflex via hindlimb vascular occlusion.
- Maintained constant heart rate using a pacemaker to isolate stroke volume changes.
Main Results:
- Muscle metaboreflex activation increased systemic arterial pressure, heart rate, and cardiac output.
- Stroke volume remained unchanged during reflex activation with normal heart rate.
- With heart rate held constant, stroke volume significantly increased, maintaining cardiac output and arterial pressure.
Conclusions:
- Muscle metaboreflex activation enhances ventricular contractility.
- Sustained stroke volume, coupled with increased heart rate, contributes to elevated cardiac output.
- These findings highlight the importance of ventricular contractility in the muscle metaboreflex response.