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Autonomic nervous system responses to exercise in relation to ventilatory threshold.
Y Yamamoto1, R L Hughson, Y Nakamura
1Department of Kinesiology, University of Waterloo, Ontario, Canada.
Chest
|May 1, 1992
Summary
This study reveals how autonomic nervous system activity, specifically parasympathetic and sympathetic nervous system (PNS and SNS) function, changes during exercise relative to the ventilatory threshold (Tvent). Findings link reduced PNS and increased SNS activity above Tvent to less complex autonomic dynamics.
Area of Science:
- Cardiology
- Autonomic Neuroscience
- Exercise Physiology
Background:
- Heart rate variability (HRV) reflects cardiac autonomic nervous system (ANS) activity, including parasympathetic (PNS) and sympathetic (SNS) influences.
- HRV analysis, particularly spectral analysis and fractal dimension (DF), can assess ANS complexity.
- The ventilatory threshold (Tvent) is a key indicator of exercise intensity and physiological stress.
Purpose of the Study:
- To investigate the relationship between ANS control of heart rate during exercise and the ventilatory threshold (Tvent).
- To examine how PNS and SNS activity, along with ANS complexity (fractal dimension), change in relation to Tvent.
- To explore the implications of these findings for clinical cardiology.
Main Methods:
- Utilized heart rate variability (HRV) spectral analysis to assess autonomic nervous system (ANS) activity.
- Measured changes in parasympathetic (PNS) and sympathetic (SNS) nervous system indicators, including plasma norepinephrine and epinephrine concentrations.
- Analyzed the fractal dimension (DF) of HRV time series to evaluate ANS complexity.
- Correlated HRV parameters with the ventilatory threshold (Tvent) during exercise.
Main Results:
- Parasympathetic nervous system (PNS) activity was significantly reduced below the ventilatory threshold (Tvent).
- Sympathoadrenal activity indicators (plasma norepinephrine, epinephrine, and SNS indicator) showed an enhanced rate of change above Tvent.
- Changes in PNS and SNS indicators were associated with the emergence of low-dimensional (low DF) dynamics, suggesting reduced autonomic complexity.
Conclusions:
- Autonomic nervous system (ANS) regulation of heart rate exhibits distinct patterns below and above the ventilatory threshold (Tvent) during exercise.
- The transition above Tvent is characterized by decreased parasympathetic and increased sympathetic nervous system (SNS) activity, coupled with reduced autonomic complexity.
- These findings offer insights into exercise physiology and may have implications for clinical cardiology, particularly in assessing cardiovascular health and stress responses.