Glossary
HRV biofeedback
Also called resonance breathing, resonance frequency breathing, HRVB
A breathing practice in which you watch your heart rate live and breathe slowly, often near 6 breaths a minute, to make the heart's rise and fall with each breath as large as possible.
Your heart speeds up a little when you breathe in and slows when you breathe out. HRV biofeedback (HRVB) trains you to make that swing as big and smooth as possible. You breathe slowly while a screen shows your heart rate beat by beat, and you try to turn it into a steady wave of peaks and valleys that matches your breathing.
For most people, the largest swings come at about 0.1 Hz, roughly 6 breaths a minute. At that pace, heart rate and breathing move exactly in step. Lehrer and Gevirtz explain this as resonance: the breathing rhythm lines up with a natural rhythm of the baroreflex, the system that steadies blood pressure. The best pace differs a little from person to person. Later work put the average closer to 5.5 breaths a minute, and taller people and men tend to have slightly lower resonance rates.
Researchers have studied HRVB for a wide range of conditions, from asthma to depression, and the leading explanation for any benefit is a stronger baroreflex. It should not replace medical care.
Slow breathing also changes HRV during the session itself. Breathing at about 0.1 Hz puts the breathing rhythm inside the LF LF power The share of heart rate variability in slow rhythms of 0.04 to 0.15 Hz, about one cycle every 7 to 25 seconds. Once read as sympathetic activity, which is now disputed. More about LF power band, so LF power rises sharply. That is expected and does not mean stress. If you want your daily HRV readings to stay comparable, do not take one during a session.
The lesson The nervous system behind HRV explains the mechanism, and Can breathing exercises raise your HRV? looks at the evidence.