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Are You Parasympathetic?

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Are You Parasympathetic?

Dr. Deepesh Khanna

Heart rate variability (HRV) means changes in the interval or distance between one beat of the heart and the next (1). It has relevance for physical, emotional, and mental function. The human heart is a bio-electrical pump beating at an ever changing rate. This variability in heart rate is an adaptive quality in a healthy body. HRV is controlled by the autonomic nervous system, which is comprised of sympathetic and parasympathetic components. It has been elucidated that alterations in heart rate are brought about by simultaneous reciprocal changes in the sympathetic and parasympathetic influences on the heart. High HRV is associated with increased parasympathetic and decreased sympathetic activity (2, 3). Adaptive changes occur in the cardiovascular system as a result of regular physical exercise, mainly in sympathetic and parasympathetic system that effect heart rate during rest and exercise (4). There is a long held premise when examining HRV that an elevated resting level of sympathetic neural activity is not healthy for the heart. Several researchers also proved that reductions in the sympathetic nervous system activity for any given exercise intensity would occur in healthy individuals (5). They concluded that regular activity results in clear indication of reduced sympathetic and increased parasympathetic indicators in middle-aged adults and a significant difference is found in HRV between males and females that may influence cardiovascular health. Frequent aerobic exercise leads to a shift in autonomic neural components toward the parasympathetic (6). The significance of this shift is that an increase in parasympathetic is a sign of a healthy heart, while a reduction of the parasympathetic activity is associated with increased incidence of sudden death (6). There are available studies that have shown that exercise training can provide the necessary variability in the heart rate; just another reason why regular exercise can lead to a healthier life!


1. Akselrod S, Gordon D, Ubel FA, Shannon DC, Barger AC, Cohen RJ. Power spectrum analysis of heart rate fluctuation: a quantitative probe of beat-to-beat cardiovascular control. Science.1981; 213:220-222

2. Pomeranz B, Macaulay RJB, Caudill MA, Kutz I, Adam D, Gordon D, Kilborn KM, Barger AC, Shannon DC, Cohen RJ, Benson H. Assessment of autonomic function in humans by heart rate spectral analysis. Am J Physiol. 1985; 248:H151-H153

3. Pagani M, Lombardi F, Guzzetti S, Rimoldi O, Furlan R, Pizzinelli P, Sandrone G, Malfatto G, Dell'Orto S, Piccaluga E, Turiel M, Baselli G, Cerutti S, Malliani A. Power spectral analysis of heart rate and arterial pressure variabilities as a marker of sympatho-vagal interaction in man and conscious dog. Circ Res. 1986;59:178-193

4. Keteyian S, Brawer C, Schairer J R. (1997).  Exercise Testing and Training Patients with Heart Failure due to Left Ventricular Systolic Dysfucntion.  Journal of Cardiopulmonary Rehabilitation. 19:  19-28.

5. Hatfield B D, Spalding T W, Maria L, Porgues S W, Potts J T, Bryne E A, Brady E B, Mahon A D. (1998).  Respiratory sinus arrhythmia during exercise in aerobically trained and untrained men. Medicine & Science in Sports & Exercise.  November 1997:  206-213

6. DeMeersman R E.  (1993).  Heart Rate Variability and Aerobic Fitness.  The American Journal. 125 (3):  726-730.



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