Why We Measure Heart Rate Variability (HRV)


If you really want to make health changes for the better in 2020, there has never been a better time.

The measure of Heart Rate Variability (HRV) is potentially the most important scientific indicator of ‘wellbeing’ available to us today (1). HRV can provide important insight into your own personal ability to adapt to stress. Simply put, HRV represents an inner state which precedes many chronic health problems or optimal health and longevity.

Plus, it’s easily accessible to most smart phones.

What is HRV?

HRV is the inter-beat INTERVAL variability between successive heart contractions.

It is not heart rate, which is the average beats per minute.

If we measure our pulse and get a reading of 60 beats per minute, it doesn’t mean we have a beat every second. The time differences between beats are slightly different, they can be 0.8 seconds, 0.7 seconds, and 1.2 seconds etc. (Fig.1.) This variability is significant.

There are different ‘measurable features’ of HRV that are used to quantify this variation between heart beats. The metric (agreed by scientific community) used to monitor your ability to ADAPT to stress is called rMSSD (Root Mean Square of the Successive Differences).

Figure 1. Heart Rate Variability Chart

Why is HRV so important?

Essentially, HRV is an analysis of how well your nervous system adapts to stress, and in particular the Autonomic Nervous System (ANS).

‘Autonomic’ refers to the automatic nervous system. It’s the part of the nervous system that regulates many of the bodily functions you don’t think about like:

  • Heart rate
  • Blood pressure
  • Body temperature
  • Electrolyte balance
  • Respiratory rate

The ANS consists of two branches – the sympathetic and parasympathetic branches. The sympathetic branch is in charge of the fight or flight response, while the parasympathetic branch promotes rest and recovery. Both branches are always active to some degree, and their control of an organ depends on their balance at any given time.

Another way to explain your healthy state of balance in the ANS is ‘flexibility’. For us to be healthy, our ANS must be able to move from a state of stress, back to rest and restoration with ease… or flexibility.

High HRV is good – Low HRV is not so Good!

Generally speaking, a high measure of HRV is associated with healthy longevity and the side of the nervous system that promotes relaxation, digestion, sleep and recovery.

A low HRV reading is commonly associated with stress, overtraining and inflammation. Low HRV is also shown to precede many chronic diseases such as  diabetes, coronary heart disease and high cholesterol  (1).

Measure HRV with your Smart Phone

The modern-day smart phone is equipped with cameras and light that can measure blood flow and calculate HRV… so convenient!

The technique is called photoplethysmography (PPG for short).

There are various apps available (we’ve tried and recommend one in particular) which use the phone camera to extract PPG data and calculate HRV.

How Accurate could using your Phone be?

PPG has been used for a long time in clinical settings, and has been validated multiple times, proving to be a reliable measurement of HRV when compared to standard electrocardiograms (ECG) (2).

An ECG is the test a cardiologist or doctor may commonly use in the assessment of cardiovascular disease. It represents the heart’s electrical activity, and electrodes are placed on the skin of chest, arms, and legs (3).

That being said, phone assessment it is not a diagnostic, nor does it replace a trip to the doctor or cardiologist! If you have any concerns about your health, please seek advice from your general practitioner.

ECG is far more sensitive at assessing the space between each beat of the heart, as it takes a much more detailed sample size per second. This provides more accuracy when determining the actual peak of the heartbeat, and therefore, the distance between the two beats (or the RR interval) – see Fig. 2 – RR interval is the measurement of time between heart beats.

For our purposes, HRV can be reliably taken using a phone if done correctly, particularly if it is taken over months to establish a base line and trends in your individual ANS state.

Readings taken in isolation are less meaningful. Readings taken over multiple days reduce the chance of a single measurement skewing results.

So we recommend that you get into the habit of measuring your HRV on a daily basis.

When to Measure

HRV measurements taken at rest are most recommended because they have been heavily researched, are practically proven, and are easily trend-able.

It’s recommended that this measurement be taken in the first half hour of waking. I measure it lying down.

If you are concerned about having your phone near you at night, turn it off, or have it nearby in another room if you use it as an alarm.

HRV naturally changes throughout the day due to internal processes and external/internal stressors. Measuring first thing in the morning eliminates many variables for more consistency.

The amazing thing is it only takes one minute!

The App We Use


The HRV4Training app was recommended to me via my mentor, Dr. Adrian Wenban, who is an Epidemiologist/Chiropractor. Adrian has used this app for years and applied a simple protocol to achieve some impressive results.

Over a period of 30 months (October 2016 – April 2019), Adrian went from never having done a triathlon to making the Australian team, and coming 12th in his Age Group at the International Triathlon Union (ITU).

The benefits – no sensor is needed so throw that strap away! Plus, The research on its reliability has all been done.

HRV4Training costs between $9.99-$13.99 (depending on where you download it from), works with regular Bluetooth 4.0 sensors as well (e.g. a Polar H7 or H10), while on Android both Bluetooth 4.0 and ANT+ are supported. You can also use your Apple Watch or Oura ring to measure HRV and read it in HRV4Training,


How to Improve HRV

This is where it gets interesting! And where some really interesting and innovative lifestyle changes can be adopted and monitored to see what improves your HRV.

But first, it’s good to take a look at the ancestral model of health care to understand how our lifestyle has dramatically changed over time.

Certain lifestyle elements have been altered since hunter-gatherer times, including:

  • exposure to different extremes of temperature (we now have temperature-controlled homes and offices)
  • movement patterns (we’ve moved towards a sedentary lifestyle), and
  • availability to food (many of us eat regularly and include processed foods in our diet, so our adaptability to burning fat stores, rather than glucose, is lessened).

With these changes in lifestyle, the nervous system appears to have lost its ability to adapt, which can relate to loss of health, particularly over our lifetime.

It seems like ‘use it or lose it’ applies.

Two lifestyle modalities that have been shown to improve HRV are Intermittent Fasting and High Intensity Interval Training (HIIT) (4-5).

Intermittent Fasting is one of the most researched areas showing that our body switches on key ANS functions, increasing its adaptability.

The evidence of Interval Training continues to grow. Our ancestors were far more physical in their movements, and probably moved with much greater variability.

Adapt-Ability Workshop

If you’re interested in learning more about how to improve your adaptability, come to one of our regular Adapt-Ability Workshops (offered online during COVID-19).

  • We look at how to improve the function of the autonomic nervous system (ANS) and make it more adaptive to our life.
  • We discuss how our genetic makeup has largely come from generations as a hunter gather. During this period we required a far greater adaptive range to the elements. There is constant exposure, sometime food scarcity, a diverse amount of required movement etc. According to a growing number of research papers, our ANS ‘likes’ certain stressors such as cold exposure to be healthy! (4).
  • We’ll show you how to proactively manage your current and future health through simple and measurable strategies, including measuring your heart rate variability (HRV).
  • We’ll help you apply 9 Lifestyle Interventions that can be adapted to suit your individual situation.
  • You’ll also learn how to measure the effectiveness of those interventions on your overall wellbeing.


  1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4311559/
  2. https://www.ncbi.nlm.nih.gov/pubmed/28290720
  3. https://www.webmd.com/heart-disease/electrocardiogram-ekgs#1
  4. https://www.ncbi.nlm.nih.gov/pubmed/30018242
  5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3652955/

DISCLAIMER: All content is created and published online for informational purposes only. It is not intended to be a substitute for professional medical advice and should not be relied on as health or personal advice. Always seek the guidance of your doctor or other qualified health professional with any questions you may have regarding your health or a medical condition.

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