Characteristics of resonance in heart rate variability stimulated by biofeedback - Vaschillo et al. (2006)
Key Points
Slow breathing at resonant frequency stimulates and exercises your autonomic and cardiovascular systems, restoring balance
There is an inverse relationship between resonance frequency and height: taller people generally have a lower resonant frequency and need to breathe slower
Care must be taken not to hyperventilate while breathing at resonant frequency; this typically takes 3 sessions to achieve
The Breathing Diabetic Summary
This is another great paper on heart rate variability and slow breathing. The paper goes deeper into a subject called “resonant frequency,” and describes biofeedback approaches for achieving respiration rates at this frequency. In the end, however, they conclude that simply breathing slowly is probably good enough to get the positive benefits of resonant breathing. Let’s start by looking at what the resonant frequency is.
(There have been two great books written on breathing at your resonant frequency: The Healing Power of the Breath and The New Science of Breath. If this subject interests you, I suggest getting the books to learn more.)
Your blood pressure (BP) and heart rate (HR) are always changing in relation to each other. As one example, when you breathe in your heart rate increases and blood pressure decreases, and when you exhale your heart rate decreases and blood pressure increases. Several other processes modulate increases and decreases in HR and BP. However, these codependent changes in HR and BP do not occur simultaneously: there is a delay. This delay represents “resonance.” The frequency at which this delay happens is called the “resonant frequency.”
When we stimulate the cardiovascular system at this resonant frequency, good things happen. And one of the easiest ways to do this is by breathing at your resonant frequency. How do we determine if we are breathing at our resonant frequency? They give two criteria. First, we must maximize our HR oscillations (that is, increase heart rate variability [HRV]). Second, our heart rate must increase concurrently with our inhale and decrease concurrently with our exhale. If this does not occur, one is either breathing faster or slower than their personal resonant frequency.
To examine the characteristics of resonant frequency across both healthy and asthmatic populations, the authors used data from two previous studies with a total of 56 patients. The patients were taught to breathe at their resonant frequency using biofeedback equipment. They performed 10 sessions over ~2.5-3.5 months.
Here are some of the key findings from their analysis of resonant frequency within these patients:
The average resonant frequency corresponded to ~5.5 breaths/minute across all patients.
There was an inverse relationship between height and resonance. Taller people needed to breathe slower to achieve resonance (closer to 4 breaths/min), which was related to having more blood volume.
It took 3 breathing sessions for the participants to achieve resonant breathing without hyperventilation.
When participants do breathe at their resonant frequency, they improve HRV and baroreflex. The authors suspect that these benefits are the result of autonomic reflexes being “exercised” when breathing at one’s resonant frequency. The final outcome is better balance between the sympathetic and parasympathetic nervous systems and overall better autonomic function. (Sounds good to me!)
To summarize, breathing at one’s individual resonant frequency elicits positive benefits in the autonomic nervous system. There are two criteria to determine if you’re breathing at your particular resonant frequency (see above). However, the authors concluded that it might be good enough to just breathe slowly, at around 5.5 breaths/min, to get positive results without the need for biofeedback equipment. For us, we can practice breathing at rates of 3-6 breaths/min until we find one that feels best for us. Personally, I feel my best around 3.5–4 breaths/min. It would also be worth it to practice Breathe Light for a week or two beforehand to train yourself not to hyperventilate while breathing so slowly.
Abstract from Paper
As we previously reported, resonant frequency heart rate variability biofeedback increases baroreflex gain and peak expiratory flow in healthy individuals and has positive effects in treatment of asthma patients. Biofeedback readily produces large oscillations in heart rate, blood pressure, vascular tone, and pulse amplitude via paced breathing at the specific natural resonant frequency of the cardiovascular system for each individual. This paper describes how resonance properties of the cardiovascular system mediate the effects of heart rate variability biofeedback. There is evidence that resonant oscillations can train autonomic reflexes to provide therapeutic effect. The paper is based on studies described in previous papers. Here, we discuss the origin of the resonance phenomenon, describe our procedure for determining an individual’s resonant frequency, and report data from 32 adult asthma patients and 24 healthy adult subjects, showing a negative relationship between resonant frequency and height, and a lower resonant frequency in men than women, but no relationship between resonant frequency and age, weight, or presence of asthma. Resonant frequency remains constant across 10 sessions of biofeedback training. It appears to be related to blood volume.
Journal Reference:
Evgeny G. Vaschillo, Bronya Vaschillo, and Paul M. Lehrer, (2006) Characteristics of resonance in heart rate variability stimulated by biofeedback, Applied Psychophysiology and Biofeedback, 31 (2), 129 – 142, DOI: 10.1007/s10484-006-9009-3.