As part of our Biohacking Masterclass Series, we will explore a number of different techniques and practices to improve your daily performance. This series will range from obvious subjects like exercise and nutrition to fringe subjects like breathing techniques and sleep hygiene.
Heart rate variability (HRV) has (rightfully) become a buzzword in the fitness industry over the last few years. HRV is an extensively studied metric that is now used as a prognostic tool for cardiovascular health, longevity, adaptability to stressors, and readiness for physical activity. Heart rate variability is determined by measuring the difference between each heartbeat in milliseconds. As an over-simplified example, if your heart rate over one minute is 60bpm, you might think your heart has exactly one beat every second. In reality, your heart might beat every 0.95 seconds over one period and every 1.05 seconds over another. If you were to average those periods over a minute, you will still have 60bpm, but you would see variability between each beat. In this example, your HRV would be 100ms (1.05s-0.95s). If you’re still not convinced that you should be interested in your HRV, one study’s findings made enough of an argument for us:
In patients with a history of cardiac events, researchers discovered that low HRV values (<50ms) correlated with a 400% increase in risk of death compared to patients with HRV scores over 100ms. Further, HRV was the single strongest predictor of death even after taking into consideration factors like medications and demographics. [Kleiger]
Beyond longevity, you ought to be concerned with quality of life. A critical element of improving your quality of life is improving mental and physical performance every day. HRV is a predictor of that too. So how can you increase your HRV?
In reality, there are numerous contributing factors, but a few of the most readily adaptable are stress levels, cardiovascular fitness, diet, sleep, and your breathing. Each of these habits are highly relevant to holistic wellness, but one has significant influence over the others: breathing.
Where does breathing fit into the picture?
Breathing is a powerful regulator of the autonomic nervous system (ANS). In case you aren’t sure what that is, the ANS is broken down into two systems: parasympathetic nervous system and the sympathetic nervous system. The parasympathetic nervous system is active when you are relaxed. In this stage, you’ll have a lower heart rate, feel at rest, and have normal digestion. The sympathetic nervous system is active when you are in a state of ‘fight or flight’. The sympathetic response typically occurs around performance or when you’re in danger, and this state is characterized by a higher heart rate, ‘paused’ digestion, and altered cardiovascular function. The constantly evolving relationship between these two states of your ANS provides different stimuli to your heart. When you have a high HRV (and are well-prepared to perform/adapt), your heart is simultaneously able to listen to the “speed-up” cue from the sympathetic side and the “slow-down” cue from the parasympathetic side. In this state, you are highly ‘adaptable’. When you breathe properly, you are reinforcing a normal balance between the parasympathetic nervous system and the sympathetic nervous system.
Unfortunately, the vast majority of people in first-world countries are actually over-breathing, which leads to an overactive sympathetic response. Study after study has shown that many of the healthiest individuals (with the greatest fitness) have resting respiratory rates (RR) under 10 breaths per minute. The optimal resting RR according to these studies is actually between 4 and 6 breaths/minute with the most common sitting at 5.5 breaths/minute. In contrast, the most touted medical definition of a ‘normal’ respiratory rate in the US is 12-20 breaths per minute. As you’re reading this, I suggest you test your own ‘normal’ respiration rate using a timer.
Why is 5.5 breaths/minute the number?
Averaging 5.5 breaths/minute matches your respiratory rate with a physiological phenomenon called Mayer waves. Mayer waves are normal variations in your arterial blood pressure. Interestingly, these waves typically occur in a frequency of 0.1Hz, which is almost exactly 5.5 cycles/minute. But wait, isn’t that the same as the optimal respiratory rate? Indeed it is. This frequency, called the resonant frequency, brings synchrony to your RR and cardiovascular function. This number varies for everyone, but like we mentioned previously, the typical rate is somewhere between 4 and 6 breaths per minute. By breathing at your resonant frequency, you can increase something called respiratory sinus arrhythmia (RSA). Simplified, RSA is a reflection of the heart’s activity while breathing. When you breathe in, your heart receives cues from your sympathetic nervous system and heart rate increases, and when you breathe out, the heart receives cues from the parasympathetic side and heart rate decreases. If you can increase the range in which the heart rate increases and decreases, studies have shown that you will increase your HRV.
Before you begin practicing, make sure you understand the instructions. Improper execution can lead to hyperventilation and more detrimental effects than positive ones. While you are breathing at the resonant frequency, it is important to not breathe too deeply. A good analogy we’ve found is to imagine a feather under your nose, and neither your inhales nor your exhales should disturb the feather. Do not take a full, deep breath. Instead, breathe in calmly for 5.5 seconds, and without pausing, exhale for 5.5 seconds. Repeat this process for several minutes. If you want to see tremendous results, incorporate 20 minutes of this practice into your daily or nightly routine. Resonance breathing before bed has been shown to improve the quality of restorative sleep, which will enable you to reap the benefits of your previous day’s training and execute at a higher level the next.
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- P. Lehrer, E. Vaschillo, B. Vaschillo. Resonant frequency biofeedback training to increase cardiac variability: rationale and manual for training. Appl. Psychophysiol. Biofeedback, 25 (3) (2000), pp. 177-191
- E. Vaschillo, B. Vaschillo, P. Lehrer. Characteristics of resonance in heart rate variability stimulated by biofeedback. Appl. Psychophysiol. Biofeedback, 31 (2) (2006), pp. 129-142
- J.M. Del Pozo, R.N. Gevirtz, B. Scher, E. Guarneri. Biofeedback treatment increases heart rate variability in patients with known coronary artery disease. Am. Heart J., 147 (3) (2004), p. 545545
- M. Sakakibara, J. Hayano, L.O. Oikawa, M. Katsamanis, P. Lehrer. Heart rate variability biofeedback improves cardiorespiratory resting function during sleep. Appl. Psychophysiol. Biofeedback, 20 (2013), pp. 1-7
- Steffen PR, Austin T, DeBarros A, Brown T. The Impact of Resonance Frequency Breathing on Measures of Heart Rate Variability, Blood Pressure, and Mood. Front Public Health. 2017;5:222. Published 2017 Aug 25. doi:10.3389/fpubh.2017.00222
- Senthilnathan S, Patel R, Narayanan M, et al. An investigation on the influence of yogic methods on heart rate variability. Ann Noninvasive Electrocardiol. 2019;24(1):e12584. doi:10.1111/anec.12584
- Lin IM, Tai LY, Fan SY. Breathing at a rate of 5.5 breaths per minute with equal inhalation-to-exhalation ratio increases heart rate variability. Int J Psychophysiol. 2014 Mar;91(3):206-11.