Four Heart Rate Variability Myths

Updated: Aug 14

Four HRV myths are Heart Rate Variability Is Bad, Stability Is Good, The Sympathetic Nervous System Plays a Major Role in Short-Term HRV, The Goal of HRV Biofeedback Is To Increase Low-Frequency Power At Rest, and Longer Exhalations Increase HRV. Heart Rate Variability Is Bad, Stability is Good "We want a relatively stable average heart rate, but high variability of instantaneous heart rate" (Khazan, 2022).

"A healthy heart is not a metronome" (Shaffer, McCraty, & Zerr, 2014). When the time intervals between heartbeats significantly change across successive breathing cycles, this shows that the cardiovascular center can effectively modulate vagal tone. "The complexity of a healthy heart rhythm is critical to the maintenance of homeostasis because it provides the flexibility to cope with an uncertain and changing environment . . . HRV metrics are important because they are associated with regulatory capacity, health, and performance and can predict morbidity and mortality" (Shaffer, Meehan, & Zerr, 2020). The Sympathetic Nervous System Plays a Major Role in Short-Term HRV We measure short-term HRV over ~ 5 minutes. Respiratory sinus arrhythmia (RSA), the baroreceptor reflex, and the vascular tone rhythm are the most important sources of HRV (Hayano & Yuda, 2019; Vaschillo et al., 2002). None of these processes are sympathetic. Respiratory sinus arrhythmia (RSA), HR speeding and slowing across each breathing cycle, is the primary and entirely parasympathetic source of HRV. The baroreceptor reflex, which exerts homeostatic control over acute BP changes, is the second most important and entirely parasympathetic source of HRV. The vascular tone (VT) control system regulates arteriole (small muscular artery) diameter. The Goal of HRV Biofeedback Is To Increase Low-Frequency Power At Rest We train clients to increase low-frequency (LF) power using slow-paced breathing to increase high-frequency (HF) power during normal breathing (i.e., 12-16 bpm). Let's unpack this. Paced breathing at ~ 6 bpm increases RSA, stimulating the baroreflex. Months of practice increase vagal tone measured by the natural log of HF power when breathing at typical rates (Gevirtz, Lehrer, & Schwartz, 2016).

Longer Exhalations Increase HRV Many professionals encourage clients to exhale longer than they inhale. There is no doubt that some clients prefer longer exhalations. The jury is still out on whether this breathing pattern is healthier. However, there is overwhelming evidence that it does not increase time-domain, frequency-domain, or nonlinear HRV measurements (Zerr et al., 2015; Meehan et al., 2018; Shaffer & Meehan, 2022). Summary The verdict is "false" for all four HRV myths: (1) HRV is good, equal interbeat intervals are bad. (2) The parasympathetic nervous system generates short-term HRV. (3) HRV biofeedback aims to increase the natural log of HF power at rest. (4) Longer exhalations do not increase any HRV metric. References Gevirtz, R. N., Lehrer, P. M., & Schwartz, M. S. (2016). Cardiorespiratory biofeedback. In M. S. Schwartz & F. Andrasik (Eds.). Biofeedback: A practitioner’s guide (4th ed.). The Guilford Press. Hayano, J., & Yuda, E. (2019). Pitfalls of assessment of autonomic function by heart rate variability. Journal of Physiological Anthropology, 38, 3. Khazan, I. Z. (2022). HRV myths. HRV Biofeedback Bootcamp. Association for Applied Psychophysiology and Biofeedback. Meehan, Z., Muesenfechter, N., Gravett, N., Watson, T., Smith, A., Shearman, S., Bartochowski, Z., West, A., & Shaffer, F. (2018). A 1:2 inhalation-to-exhalation ratio does not increase heart rate variability during 6-bpm breathing [Abstract]. Applied Psychophysiology and Biofeedback, 43, 109–111. https:// doi. org/ 10. 1007/s10484-018-9390-8 Shaffer, F., McCraty, R., & Zerr, C. L. (2014). A healthy heart is not a metronome: An integrative review of the heart’s anatomy and heart rate variability. Frontiers in Psychology. doi:10.3389/fpsyg.2014.01040 Shaffer, F., & Meehan, Z. M. (2022). An undergraduate program with heart: Thirty years of Truman HRV research. Applied Psychophysiology and Biofeedback.

Shaffer, F., Meehan, Z. M., & Zerr, C. L. (2020). A critical review of ultra-short-term heart rate variability norms research. Frontiers in Neuroscience. Vaschillo, E., Lehrer, P., Rishe, N., & Konstantinov, M. (2002). Heart rate variability biofeedback as a method for assessing baroreflex function: A preliminary study of resonance in the cardiovascular system. Applied Psychophysiology and Biofeedback, 27, 1-27. Zerr, C., Kane, A., Vodopest, T., Allen, J., Hannan, J., Fabbri, M., Williams, C., Cangelosi, A., Owen, D., Cary, B., & Shaffer, F. (2015). Does inhalation-to-exhalation ratio matter in heart rate variability biofeedback? [Abstract]. Applied Psychophysiology and Biofeedback, 40, 135.

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