What is Heart rate variability (HRV)?

Have you ever seen an electrocardiogram (ECG) trace before? You might have come across it in a movie whereby its activity became flatline signalling the unfortunate death of a patient. Essentially, HRV measures the variability between beat to beat of the R-R wave interval (see below).

HRV analysis is a non-invasive measurement of the autonomic nervous system.

 

If you’re not familiar with the nervous system, there are two branches. There’s the central nervous system—the brain and the spinal cord. Then there’s the autonomic nervous system. One is called the “fight or flight” branch of the sympathetic nervous system. The other is the “rest and digest” branch of the parasympathetic nervous system.

 

The sympathetic system is how the body mobilizes energy. The sympathetic system increases heart rate. It raises blood pressure. It diverts blood flow to the working muscles. It releases sugar throughout the bloodstream and inhibits digestion. It reduces appetite.

It does all these things to get us ready to produce energy and to get energy flowing to the working muscles.

It’s called “fight or flight” because it’s literally preparing the body for fight or flight—that adrenaline rush.

The other branch is called the parasympathetic system. It’s the opposing system. It slows down heart rate. It decreases blood pressure. It dilates blood vessels. It promotes energy going back to where it came. It stimulates digestion and appetite.

It does everything to get us back to a normal state—rest, repair, adjust or remodel.

These two systems work together at the core of homeostasis and allostasis. These two systems are kind of the strings of the puppet master, the brain, pulls to make sure homeostasis is always maintained – ensuring your body has the energy it needs at all times. If you’re working muscles, you need more energy, so the sympathetic system cranks up. It increases heart rate and blood pressure. It’s going to deliver more oxygen to those muscles. It’s going to divert energy there. When you’re done, it’s going to put everything back. It sets heart rate back down to normal and gets us back to where we were to stimulate the anabolic processes to rebuild and remodel. These are the two systems the body uses to coordinate the response to stress and how it responds to what we do to it. Each one of those systems will have an impact on the rhythm of the heart rate, but it’s mostly the parasympathetic system that causes variability in heart rhythm pattern.

People believe the heart is like a metronome and that it beats at a very regular interval—but the reality is, it doesn’t! The heart beats in an irregular pattern and that has to do with the influence of the parasympathetic system.

Just gain some appreciation as to how HRV is maintained (below). HRV is determined by the heart and 3 levels of the brain “talking” to each other, whereby other various bodily systems (renal, endocrine, digestive & immune) play somewhat a mediating role between these 2 connections:

Stress, as depicted below, comes from many sources!

Below are two definitions that are useful to know when it comes to measuring stress on a biological system:

Homeostasis – The tendency toward a relatively stable equilibrium between interdependent elements, especially as maintained by physiological processes.

Allostasis – The process of achieving stability, or homeostasis through physiological or behavioural change.

With reference to HRV, we can get tremendous insight into what the body is doing, how the body is responding to training and how it’s reacting based on everything the person might be doing.

The more strongly the parasympathetic system—the rest and digest system—is activated, the more variable the heart rate becomes and the more we see variability in the pattern of the heart rate. The less active it becomes, the more the sympathetic system becomes dominant. There is less change from one beat pattern to the next. By looking at that pattern—by looking at the shape of the heart rhythm, seeing what it looks like and performing some math on it—we can get an idea of how much the parasympathetic system is activated at any point. When we see one particular pattern of heart rhythm, we see a sympathetic dominant pattern and we know something is going on. If we see a parasympathetic pattern, we know the body is in a different state. If you want to look at this simply, that’s what heart rate variability does. This tells us a lot about how the body is doing, whether or not the training program is headed in the right direction, headed toward the over-reached or over-trained state or right on track.

If we see the body chronically under too much stress and we see a particular pattern where the sympathetic system is always on, we know the person is having a hard time resting and getting back to normal. We know the body is shifting that sympathetic load for a reason. We make training adjustments to bring down those stressors and to promote the parasympathetic system. If we see the opposite with too much parasympathetic activity, that generally is more of a deeply over-trained state where the body has shut down its response to stress. It’s no longer able to respond the way it should. By looking at how these two systems are functioning and where the balance lies between the two, we can get a very specific idea of where somebody is on the training continuum. We can get a very good idea of what changes we need to make to the program.

Measuring HRV may determine what stage of the GAS stage you are in! whether it be due to a high volume/acute novel exercise stressor or other various cumulative stressors.

So, what does the research say?

Changes in HRV have been correlated to many leading causes of death including

  • Heart disease
  • Cancer
  • Chronic lower respiratory disease
  • Stroke (cerebrovascular disease)
  • Alzheimer’s disease
  • Diabetes
  • Influenza and pneumonia
  • Renal disease

Most clinics typically measure both resting and exercising heart rate as a measure of stress. However, HRV Kubios and Nerve Express are the only systems worldwide that assess and quantify the balance between the sympathetic and parasympathetic nervous systems during: 1) breath holding-deep breathing manoeuvres; 2) supine to standing and 3) during exercise. Without going into much detail, these 3 points illustrate the health status, fitness capacity and adaptability of your bodily system. It gives us an idea of what your body is doing, whether it’s under acute stress or whether it’s repairing, regenerating or remodelling from stress. We can provide this in the comfort of The Chiro Hub!

Dr. Yazbek has undertaken extensive HRV training that allows him to assess, analyse and identify HRV data and convey all of the most relevant, appropriate and meaningful information for you, in order to take control of your current state of health. Make an appointment HERE now!

References:

  1. Koenig, J., Williams, Kemp,  D. P., Thayer, J. F. (2016), Vagally mediated heart rate variability in headache patients – a systematic review and meta-analysis; Cephalagia, 36(3), 265-78.
  2. Christensen, J. H., Toft, E., Christensen, M. S. and Schmidt, E. B.(1999) Heart Rate Variability and plasma lipids in med with and without ischaemic heart disease, Atherosclerosis, 145(1), 181-6.
  3. Wulsin, L. R., Horn, P. S, Perry, G. L., Massaro, J. M., D’Agostino, R. B. (2015), Autonomic Imbalance as a Predictor of Metabolic Risks, Cardovascular Disease, Diabetes, and Mortality, Journal of Clinical Endocrinal Metabolism, 100(6), 2443-8.
  4. Aeschbacher, S., Bossard, M., Schoen, T., Schmidin, D., Muff, C., Maseli, A., Leuppl, J. D., Miedinger, D., Probst-Hensch, N. M, Schmidt-Trucksass, A., Risch, M., Riach, L and Conen, D. (2016), Heart Rate Variability and Sleep-Related Breathing Disorders in the General Population, American Journal of Cardiology, S002-9149(16), 31103-1.
  5. Shah, A. J., Lampert, R., Goldberg, J., Veledar, E., Bremner, J. D and Vaccarino, V. (2013), Posttraumatic stress disorder and impaired autonomic modulation in male twins, Biological Psychiatry, 73(6), 475-82.
  6. Shah, A. J., Su. S., Veledar, E., Bremner, J. D., Goldstein, F. C., Lampert, R., Goldberg, J.and Vaccarino, V. (2011), Is heart rate variability related to memory performance in middle-aged men?, Psychosomatic Medicine, 73(6), 475-82
  7. Schroeder, E. R., Lioao, D., Chambless, L. E., Prineas, R. J., Evans, G. W. and Heiss, G., (2003), Hypertension, blood pressure, and heart rate variability: the Atherosclerosis Risk in Communities (ARIC) study, Hypertension, 42(6), 1106-11.

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