Heart Rate Variability:
Your Body’s Built-In Resilience Gauge
Why HRV Matters More Than You Think
Based on insights from Dr. Inna Khazan
Heart Rate Variability (HRV) isn’t just a quirky heart pattern, it’s a great window we have into the health of your nervous system. It reflects how adaptable your body is to stress, how quickly you can recover, and how efficiently you can perform - whether that’s on stage, in the field, or at your desk.
According to Dr. Inna Khazan, a Harvard Medical School faculty member, author, and leading biofeedback expert, HRV is a direct measure of resilience. The higher and more flexible your HRV, the better your body can keep you in that “sweet spot” of alertness - energized but not overstimulated.
What Is HRV? It Matters More Than You Think!
HRV measures the subtle variation in time between heartbeats, recorded in milliseconds.
Even if your average heart rate is steady (e.g., 70 beats per minute), the exact spacing between beats changes constantly.
Two people can have the same average heart rate but:
High HRV - large swings between fastest and slowest beats (healthy, adaptable)
Low HRV - very little change between beats (rigid, less resilient)
Overall, HRV reflects the ability of the autonomic nervous system to regulate itself.
Why It’s So Powerful
For decades, HRV was ignored or misunderstood. Now we know it’s a key biomarker for:
Cardiovascular health - A better long-term predictor than blood pressure or cholesterol (Tsuji et al., 1996).
Brain health - HRV biofeedback can improve cognition and even Alzheimer’s biomarkers (An et al., 2020).
Performance - Higher HRV supports faster reaction time, better decision-making, and quicker recovery (Forte, Favieri & Casagrande, 2019).
Mental health conditions - From anxiety and PTSD to chronic pain, HRV training has documented benefits (Lehrer et al., 2020).
The Physiology Behind HRV
Two main sources drive HRV:
Baroreflex - Regulates blood pressure by adjusting heart rate and vagal tone.
Respiratory Sinus Arrhythmia (RSA) - Heart rate rises during inhalation and falls during exhalation, mediated by the vagus nerve.
The interaction of these two systems keep your nervous system balanced.
How We Measure It
HRV can be measured in different ways, and can incorporate different time domain measures:
Standard Deviation of Normal to Normal Interval (SDNN) - Overall variability
Root Mean Square of Successive Differences (RMSSD) - More specific to parasympathetic (rest-and-digest) activity. This is often more resilient to artifact and best to use in home devices where artifacts may be higher.
Max–Min - Difference between highest and lowest heart rate within a cycle
Frequency-domain analysis - Breaks HRV into high, low, and very low frequency bands
Training HRV with Resonance Frequency Breathing
One of the most effective ways to improve HRV is resonance frequency breathing—breathing at a slow, consistent rate (usually 3.5–7 breaths per minute for adults) that maximizes heart rate oscillations.
How it works:
Like pushing a swing in perfect rhythm, your breath “pushes” your heart rate into a smooth up-and-down pattern.
Technique:
Shift your breath to the belly (“low” breathing).
Inhale gently through the nose.
Exhale slowly through the nose or pursed lips (instead of an open mouth).
Aim for about 40% inhale / 60% exhale.
Integrating HRV with Neurofeedback
HRV training is an awesome standalone practice, but can also elevate other modalities, like neurofeedback by:
Improving baseline ability to self regulate - by regulating the autonomic nervous system, the client is able to make much better use of the neurofeedback training.
Reducing anxiety and muscle tension - anxiety during neurofeedback may result in sweat that can interfere with getting a good EEG signal. Additionally, excess muscle tension will result in artifacts that can thwart the training process. HRV enables the client to reduce anxiety and relax their bodies before entering into neurofeedback.
Improving brain connectivity - one goal of neurofeedback is to improve neural connectivity, which improves with a regulated nervous system.
Improving attention and learning - HRV improves attention and learning which are essential skills for neurofeedback.
Using resonance frequency breathing to improve alpha power - especially if the goal of neurofeedback is to increase alpha to support calmness, HRV provides a great foundation for neurofeedback.
HRV training is more than a wellness trend - it’s a proven way to build resilience from the inside out. Just a few minutes a day can help you regulate stress, think more clearly, and perform at your best, all while supporting your long-term heart and brain health.
What the full Discussion Round:
References:
An, E., Nolty, A. A. T., Amano, S. S., Rizzo, A. A., Buckwalter, J. G., & Rensberger, J. (2020). Heart rate variability as an index of resilience. Military Medicine, 185(3-4), 363–369. https://doi.org/10.1093/milmed/usz325
Forte, G., Favieri, F., & Casagrande, M. (2019). Heart rate variability and cognitive function: A systematic review. Frontiers in Neuroscience, 13, Article 710. https://doi.org/10.3389/fnins.2019.00710
Lehrer, P., Kaur, K., Sharma, A., Shah, K., Huseby, R., Bhavsar, J., Sgobba, P., & Zhang, Y. (2020). Heart rate variability biofeedback improves emotional and physical health and performance: A systematic review and meta-analysis. Applied Psychophysiology and Biofeedback, 45(3), 109–129. https://doi.org/10.1007/s10484-020-09466-z
Tsuji, H., Larson, M. G., Venditti, F. J. Jr., Manders, E. S., Evans, J. C., Feldman, C. L., & Levy, D. (1996). Impact of reduced heart rate variability on risk for cardiac events: The Framingham Heart Study. Circulation, 94(11), 2850–2855. https://doi.org/10.1161/01.cir.94.11.2850