Testing the vagal withdrawal hypothesis during light exercise under autonomic blockade: a heart rate variability
Timothée Fontolliet1, Vincent Pichot2, Aurélien Bringard1
1Départements d'Anesthésiologie, de Pharmacologie et des Soins Intensifs/des Neurosciences Fondamentales, Université de Genève, Geneva, Switzerland.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|October 12, 2018
Summary
Vagal tone withdrawal causes the disappearance of heart rate variability (HRV) during exercise. This study confirms that suppressing vagal activity is key to the rapid cardiovascular response at exercise onset.
Area of Science:
- Cardiovascular Physiology
- Autonomic Nervous System Function
- Exercise Physiology
Background:
- Heart rate variability (HRV) analysis is crucial for understanding autonomic nervous system (ANS) control.
- Vagal tone withdrawal is hypothesized to occur at exercise onset, but direct evidence under autonomic blockade is lacking.
Purpose of the Study:
- To investigate the role of vagal tone withdrawal in the disappearance of HRV during exercise.
- To test specific hypotheses regarding changes in total power (PTOT) under different autonomic blockade conditions.
Main Methods:
- First analysis of HRV at rest and during exercise under full autonomic blockade (atropine and metoprolol) in the same subjects.
- Continuous recording of heart rate and arterial blood pressure.
- Power spectral analysis for HRV and blood pressure variability; sequence method for baroreflex sensitivity.
Main Results:
- Vagal blockade (atropine) significantly decreased total power (PTOT) and HRV components (LF, HF) at rest and during exercise.
- Full autonomic blockade mirrored the effects of vagal blockade on HRV.
- Baroreflex sensitivity decreased with vagal blockade at rest and during exercise.
Conclusions:
- Vagal suppression is directly responsible for the disappearance of spontaneous HRV during exercise.
- This finding supports the hypothesis of vagal withdrawal's critical role in the immediate cardiovascular adjustments to exercise onset.
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