The main purpose of breathing is gas exchange – to expel carbon dioxide and bring in fresh oxygen. Blood circulates through the lungs as the body’s gas transporter, making the exchange in the tiny pockets within the lungs. Adaptations in the circulatory system – the network of arteries, veins, and capillaries which extend to every millimeter of the body – are therefore inextricably linked to adaptations in the respiratory system. It might not be surprising then, that breathing, a process we have direct control over, has influence over our heart rate, a process we have no direct control of. But it wasn’t until 1983 that we discovered just how interconnected these two systems are.
Just over forty years ago, Evgeny Vaschillo, a scientist running a study for the Russian space program, asked a group of astronauts to increase the swings in their heart rate as they watched a live stream of their heart rate on a screen. Through controlled breathing they were able to generate swings up to 60 beats per minute, an effect so unexpected one reviewer of the journal paper thought the data had been faked [1]. But the results were correct, and the phenomenon was named resonance breathing. It was by breathing at a constant frequency between 4.5 and 6.5 breaths per minute, specific to each person, that the astronauts were able to create this resonance effect and generate a massive spike in heart rate variability.
Using the same process with a heart rate monitor you can determine your resonance breathing frequency. Start by breathing at 6.5 breaths per minute following a breathing pacer circle that expands and contracts in time with your target rate, while viewing your heart rate on a live graph. Every two minutes, decrease the pacer rate by 0.5 breaths per minute until it reaches 4.5 [3]. Review your heart rate variability at each breathing rate. Your resonance frequency is the rate where HRV is at a maximum. In the four decades of research since it was first discovered, this simple technique has been shown to have wide ranging benefits, from anxiety management to the optimisation of athletic performance [2].
The benefits of resonance breathing are because of the restorative effect it has on the autonomic nervous system (as explained in our previous article), and the two mechanisms that underlie it link our respiratory and circulatory systems. These are called respiratory sinus arrhythmia and the baroreflex, and both produce the effect of raising heart rate during inhalation, and lowering heart rate during exhalation [4]. These two reflexes are there to respond to two important things that happen when you breathe in: oxygen availability increases and blood pressure drops. Respiratory sinus arrhythmia is the reflex that signals the heart to increase flow, maximising gas exchange when the lungs are full. At the same time, blood pressure is at its lowest because of the increased volume in the chest. Pressure receptors in the blood vessels signal the drop in pressure, stimulating the baroreflex – the response to increase heart rate to maintain adequate circulation to the body. We don’t have direct control over our heart beat, but respiratory sinus arrhythmia and the baroreflex give us influence over our heart rate through breathing.
Breathing to influence heart rate is like pushing someone on a swing – you can’t control the motion exactly, but can set swings in motion, and control the height of each swing. And when the timing of each push is just right you get a resonance effect where it becomes effortless to keep swinging. Pushing too early or too late, however, dampens the swing. Likewise, breathing precisely at your natural resonance effortlessly maximises heart rate swings. It has furthermore been shown that the benefits of deep, slow breathing are increased at this rate [3], and mimics the state achieved in eastern meditative practices [5]. With Heartspace you can find your resonance breathing frequency in 10 minutes and in this video, Kieran, Co-founder of Heartspace shows you how:
References
- Lehrer, P. (2013). How does heart rate variability biofeedback work? Resonance, the baroreflex, and other mechanisms. Biofeedback, 41(1), 26-31
- Lehrer, P. M., & Gevirtz, R. (2014). Heart rate variability biofeedback: how and why does it work?. Frontiers in psychology, 5, 104242.
- Shaffer, F., & Meehan, Z. M. (2020). A practical guide to resonance frequency assessment for heart rate variability biofeedback. Frontiers in Neuroscience, 14, 570400.
- Sevoz-Couche, C., & Laborde, S. (2022). Heart rate variability and slow-paced breathing: when coherence meets resonance. Neuroscience & Biobehavioral Reviews, 135, 104576.
- Lehrer, P., Sasaki, Y., & Saito, Y. (1999). Zazen and cardiac variability. Psychosomatic medicine, 61(6), 812-821.