HEART RATE VARIABILITY
What does it mean and why should I monitor it?

We love to monitor our progress and achievements when it comes to exercises and wellbeing. From making sure we hit 10,000 steps a day, keeping track of calories or using a heart rate monitor to measure the effectiveness of our workouts, it’s something many gym-goers like to keep tabs on.

Monitoring our progress in the ways above can be hugely useful, but these more traditional markers fail to take into account important factors such as sleep quality, stress levels, daily nutrition and effort exerted in recent workouts. Sometimes, we are in tune enough with our own body to accurately assess our body’s current health and ability to perform. At other times, our bodies warning signs to take it easy are so subtle and small that you can’t be aware of them consciously. This is where Heart Rate Variability (HRV) comes into its own.

Heart Rate Variability (HRV) isn’t anything new - in fact, it has been used since the 1940s. However, as technology continues to advance, it is becoming much more accessible to the everyday consumer. Used by professional sports teams and the US military, HRV is a reliable method to check how healthy our bodies are at a given moment. It can help to determine how ready a person is to exercise and identify days when rest and recovery are needed. It can be used to maximise workouts and can even predict illnesses!


What is HRV?

An ECG machine in a hospital measures the number of heartbeats per minute. With HRV, we are not interested in the number of heartbeats, but instead the time, in milliseconds, in between each beat.

If, for example, your heart rate is 60 beats per minute, that doesn’t mean your heart is beating steadily at 1 beat per second. Between each beat, the pause might vary from 0.95 to 1.05 milliseconds. The difference between each heartbeat may only be tiny, but it gives us an important insight into how your body is performing, something you may not be aware of.


How does it work?

HRV is used to measured how well your nervous system is functioning, specifically our autonomic nervous system. Our autonomic system is exactly what its name suggests - automatic. We constantly use this system in our day-to-day lives without any conscious thought. Some examples of how we use this system include breathing regulation, pupil dilation and food digestion. Our autonomic system is made up of a sympathetic and parasympathetic branch, which work in tandem to keep us balanced between high stress states and relaxed, recovery states.

Source: Tyrone Pierce, 2014, The Autonomic Nervous System (Ch 13).


Sympathetic

This is often referred to as our “fight or flight” division. It consists of a stress response, providing the body with heightened senses and a rush of energy to respond to high-pressure situations. It helps our bodies prepare for exertion, both physical and mental, such as exercise, a pressing work deadline or presenting in front of an audience. Ever given a speech or presentation and felt your heart race and mouth go dry? Your sympathetic division is in full swing.

Unfortunately, the body can overreact to stressors, such as traffic jams, work pressure, and family difficulties. If this is not managed well, it can lead to chronic stress, which in turn can result in illness, high blood pressure, loss of sleep and a series of other negative side effects.


Parasympathetic

The parasympathetic is the opposite of our sympathetic branch and can be thought of as our “rest and digest” division. It helps to restore balance in our bodies after exertion. Unsurprisingly, it is the most dominant system during sleep and relaxation.

To remember the difference between the two, it can be helpful to think of our sympathetic division as our accelerator - we use this to move. Our parasympathetic division, on the other hand, is our brake - used to slow things down. Our autonomic system is constantly adjusting the balance between the two systems, as we speed up and slow down. Depending on what we’re doing, we may at any given moment rely more on the sympathetic or parasympathetic branch. Crucially, this creates variability in our heart rate. From this, you can begin to understand how our HRV can translate to how well our bodies are functioning.

Let’s use an example. Consider the nervous system of someone who is constantly on the go, rushing around non-stop from meeting to meeting, grabbing a bite to eat if and when possible and rushing to their training sessions with only a few minutes to spare? Are they using their brake effectively? Probably not!

An imbalance in ones autonomic system, whereby the sympathetic branch is in overdrive, could have a negative impact on a person’s health if sustained over a long period of time. It is likely to affect sleep, digestion and the immune system, eventually resulting in illness. The lack of pushing and pulling between the two divisions will reduce your HRV, meaning the time between one heart beat and the next stays consistently pretty similar. A HRV monitor would pick up on this and indicate that this person needs more rest and recovery time in order for the nervous system to restore balance and work effectively.


Why Monitor HRV Data?

HRV helps us understand how our bodies need to be treated day-to-day. Are you overtraining and overusing your sympathetic division? Or are you well rested, with a great balance between the parasympathetic and sympathetic divisions? If it’s the former, then a rest day may be in order, but if it’s the latter then you may be ready to take on a tougher workout and push yourself harder.

To illustrate HRV, I took two HRV readings using my Myzone heart rate monitor and an app called Elite HRV. There are several different ways of using tech to track our HRV, but I took mine first thing in the morning, as research suggests that this is the optimum time to do so. Sticking to a consistent time of day helps to eliminate variances in factors such as digestion, stress, heart rate and air environment, all factors that simulate our nervous system and affect HRV.

Source: Elite HRV (Heart Rate Variability App).


The results from your HRV monitor can help you determine what is the best time of day to train for your body and it can help you understand when you need a more recovery-focused session and when to go all out with high intensity or heavy strength training.


How to correct your HRV?

It is important to have a healthy balance of “rest and digest” and “fight or flight”. It today’s modern age, there is often a tendency to spend too much time in a stressed state. Fortunately, people can learn techniques to counter the stress response.

1. Relaxation

Relaxation is an effective way to counteract the stress response. There are various approaches to relaxation and the best approach is simply the one that suits you best. Examples include deep abdominal breathing, visualisation of tranquil scenes of peace and calm, yoga, meditation and tai chi.

2. Exercise

We have mentioned exercises as part of the sympathetic “fight” division, but it can also be used to reduce the build up of stress. For example, taking a brisk walk when feeling stressed can help by deepening your breathing and relieving muscle tension. Movement therapies such as yoga, tai chi and qi gong combine fluid movements with deep breathing and mental focus, all of which can be incredibly effective at inducing calm. Equally, taking time in the gym to focus on flexibility and mobility - often overlooked - can be an effective use of your training time. Using a session to go over technique using lighter weights will bring blood flow to muscles to aid recovery and increase oxygen flow to both brain and body.

3. Socialising

Socialising and spending time with loved ones are great ways to unwind and relax. Maintaining close relationships with family and friends also provides an important emotional support that indirectly helps through times of chronic stress and crisis.

4. Sleep

Getting more sleep can be hugely beneficial to your to mental health, productivity and muscle growth. It may sound counterintuitive, but muscles don’t actually grow while working out, they grow in between workouts. For this reason, adequate recovery time is incredibly important. Recovery needs to consist of sufficient rest and relaxation, combined with correct nutrition.


Scientists count anything less than seven hours’ sleep as sleep deprivation, with eight hours a night being the recommended target. Research has found links between sleep loss and, among other things, Alzheimer’s disease, cancer, diabetes, obesity and poor mental health. Sleep also affects our ability to understand our body's hunger signals - inadequate sleep decreases levels of the satiety-signalling hormone leptin, and increases levels of hunger.

Therefore, in terms of HRV, sufficient sleep is critical for entering the “rest and digest” division of our autonomic nervous system, to help us build muscle, recover from exercise, reduce stress hormones and increase motivation and energy for the next workout.


Key Points To Take Away

  • A greater heart rate variability means a healthier body
  • Sympathetic = “Accelerator”, associated with stress, exercise and the “fight or flight” mode. Parasympathetic = “Brake”, recovery and relaxation, also known as “rest and digest”
  • The best time to monitor heart rate variability is every morning as soon as you wake up. This way, the environment is consistent every time
  • Listen to the data and find your balance between healthy mix of hard, sweaty workouts and recovery sessions.

HRV is only just starting to enter the consumer world, but we think it could become the next big fitness gadget after step counting. Some big companies have already developed consumer devices for measuring HRV, such as the Garmin Forerunner 235 watch and Garmin Connect IQ. Equally, all you really need is a heart rate monitor (such as a wrist, chest or arm strap), which can then connect to a HRV app.


Sources:

  1. Elite HRV (Heart Rate Variability App), URL: https://elitehrv.com/
  2. Elite HRV, Compatible Devices, URL: https://elitehrv.com/compatible-devices
  3. Elite HRV Podcast, 2016, “Clinical Rehabilitation & HRV - with Greg Elliott”, URL: https://castbox.fm/episode/id409573-id18837729?utm_campaign=android_old_share&utm_medium=dlink&utm_source=android_old_share&country=gb
  4. Essentials of Heart Rate Variability for Personal Trainers, with Carmine Grieco, NSCA, URL: https://www.youtube.com/watch?v=nDwnhmehQfg&feature=youtu.be
  5. Harvard Health Publishing, 2011, “Understanding the stress response”, URL: https://www.health.harvard.edu/staying-healthy/understanding-the-stress-response
  6. OURA Crew, 2017, “What Is Heart Rate Variability And What You Can Learn From It”, URL: https://ouraring.com/heart-rate-variability-basics/
  7. Tyrone Pierce, 2014, The Autonomic Nervous System (Ch 13), URL: https://slideplayer.com/slide/6366557/
  8. Walker, M. 2017, "'Sleep should be prescribed': what those late nights out could be costing you", URL: https://www.theguardian.com/lifeandstyle/2017/sep/24/why-lack-of-sleep-health-worst-enemy-matthew-walker-why-we-sleep
Published on 07th Jan 19