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Cardiorespiratory reactions to static, isometric exercise in man.
P E Paulev1, M Pokorski, A Masuda
1University of Copenhagen, Panum Institute, Denmark.
The Japanese Journal of Physiology
|January 1, 1991
Summary
Isometric exercise causes an immediate increase in heart rate and breathing. This response is mediated by a muscle reflex affecting the nervous system, leading to significant changes in blood pressure and flow.
Area of Science:
- Cardiovascular Physiology
- Respiratory Physiology
- Exercise Physiology
Background:
- Isometric muscular contraction, such as handgrip, elicits complex physiological responses.
- Understanding the immediate cardiovascular and respiratory adjustments to isometric exercise is crucial for comprehending the body's adaptive mechanisms.
Purpose of the Study:
- To investigate the acute cardiovascular and respiratory responses to static, isometric muscular contraction in healthy men.
- To elucidate the underlying neural mechanisms responsible for these physiological changes.
Main Methods:
- Measurements included cardiac output (Q), stroke volume (SV), heart rate (HR), and respiratory variables.
- Ten healthy men performed static, isometric handgrip exercise during air breathing.
Main Results:
- An instantaneous rise in ventilation (VI) and heart rate (HR) was observed, with minimal change in cardiac output.
- Ventilation increase was attributed to a rise in tidal volume (VT) and reduced expiratory duration (TE).
- Mean arterial pressure (MAP) and total peripheral vascular resistance (TPVR) increased by 27%, suggesting widespread vascular adjustments beyond localized occlusion.
Conclusions:
- Isometric exercise triggers a rapid muscle reflex that inhibits cardiac vagal motoneurons and stimulates respiratory medullary neurons.
- The significant increase in MAP and TPVR indicates a redistribution of cardiac output, likely involving vasoconstriction in some regions and vasodilation in others, such as the skin.