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Voluntary versus reflex regulation of maximal exercise flow: volume loops
1John Rankin Laboratory of Pulmonary Medicine, Department of Preventive Medicine, University of Wisconsin, Madison.
The American Review of Respiratory Disease
|January 1, 1989
Summary
Healthy individuals can voluntarily mimic maximal exercise breathing patterns, but with excessive pressure and increased work. Accurately replicating exercise ventilation requires matching specific breathing characteristics.
Area of Science:
- Exercise Physiology
- Respiratory Mechanics
Background:
- Maximal exercise ventilation is crucial for performance.
- Understanding voluntary control of breathing during maximal exertion is key.
Purpose of the Study:
- To assess the ability to voluntarily mimic maximal exercise ventilatory output.
- To compare the physiological parameters of voluntary maximal breathing with actual exercise.
Main Methods:
- Five healthy subjects performed maximal volitional exercise.
- Measurements included flow:volume, pressure:volume loops, end-expiratory lung volume (EELV), and breathing patterns.
- Subjects later attempted to mimic these patterns at rest using visual feedback.
Main Results:
- Voluntary mimicry achieved similar flow:volume and EELV but with excessive expiratory pressures.
- Increased abdominal expiratory muscle activity and 15-40% greater ventilatory work were observed during voluntary efforts.
- Maximal voluntary ventilation (MVV) resulted in increased EELV and 20-300% higher ventilatory work compared to maximal exercise.
Conclusions:
- Voluntary maximal breathing efforts do not perfectly replicate exercise conditions.
- Accurate assessment of maximal ventilatory output and its metabolic cost requires matching exercise-specific pressure:volume, breath-timing, and EELV.