Respiratory sinus arrhythmia (RSA) is the speeding and slowing of the heart across each breathing cycle. RSA is the primary and entirely parasympathetic source of short-term (~ 5 min) HRV. Graphic adapted from Elite Academy.
Before HRV biofeedback, respiration and the baroreflex (BR; blood pressure regulating loop) are usually out of phase resulting in weak resonance effects.
HRV biofeedback training slows breathing to the baroreflex’s rhythm, which aligns these processes and significantly increases resonance effects.
Slowing breathing at rates between 4.5-6.5 bpm for adults and 6.5-9.5 bpm for children increases RSA (Lehrer & Gevirtz, 2014). Increased RSA immediately “exercises” the baroreflex without changing the vagal tone or tightening blood pressure regulation. Those changes require weeks to months of practice.
HRV biofeedback can increase RSA 4-10 times compared to a resting baseline (Vaschillo et al., 2002). Graphic adapted from Gevirtz et al. (2016).
Summary
HRV biofeedback stimulates the baroreflex by slowing breathing to the BR rhythm. Slow-paced breathing can increase RSA 4-10 times compared with breathing at normal rates (e.g., 12-16 bpm). Changes in vagal tone and blood pressure regulation require weeks to months of practice.
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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. Lehrer, P. M., & Gevirtz, R. (2014). Heart rate variability: How and why does it work? Frontiers in Psychology. https://doi.org/10.3389/fpsyg.2014.00756 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. https://doi.org/10.1023/a:1014587304314