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Cardiopulmonary reflexes do not modulate exercise pressor reflexes during isometric exercise in humans
J A Arrowood1, P K Mohanty, C McNamara
1Department of Internal Medicine (Cardiology), Medical College of Virginia, Richmond.
Summary
Cardiopulmonary baroreflexes influence vasoconstrictor responses during isometric exercise. Reduced baroreceptor unloading (-5 mmHg lower body negative pressure) enhanced responses, while greater unloading (-10 mmHg) showed no interaction, suggesting nonlinear sympathetic control.
Area of Science:
- Cardiovascular Physiology
- Exercise Physiology
- Autonomic Nervous System Regulation
Background:
- Reflex vasoconstrictor responses during isometric exercise are modulated by arterial and cardiopulmonary baroreflexes.
- Previous research suggests baroreflexes play a key role in regulating vascular tone during physical exertion.
Purpose of the Study:
- To determine forearm vasoconstrictor responses to isometric handgrip.
- To investigate these responses during two levels of cardiopulmonary baroreceptor unloading using lower body negative pressure (-5 and -10 mmHg).
Main Methods:
- Isometric handgrip exercise performed alone and combined with -5 mmHg and -10 mmHg lower body negative pressure (LBNP).
- Measurement of forearm vasoconstrictor responses.
- Analysis of baroreflex modulation of vascular tone.
Main Results:
- Handgrip with -5 mmHg LBNP resulted in significantly greater vasoconstrictor responses than the sum of individual responses.
- -10 mmHg LBNP combined with handgrip showed no difference from the sum of individual responses.
- An interaction was noted with less baroreceptor unloading, but not with greater unloading.
Conclusions:
- The degree of cardiopulmonary baroreceptor unloading influences the interaction between isometric exercise and vasoconstrictor responses.
- These findings suggest nonlinear relationships between sympathetic nerve activity and vasoconstrictor responses, particularly at higher levels of baroreceptor unloading.