How to Use Heart Rate Variability to Get the Most From Your Training

Heart Rate Variability

Heart Rate Variability (HRV) is the measurement and comparison of the timing between heart beats and how they fluctuate day to day. HRV was developed in the 1960’s by the Russian space program. As it applies to fitness, your daily HRV measurement provides you with an assessment of your readiness to train. It tells you whether or not you should train and how hard you should train.

HRV has broad applications in a clinical setting as well. In 1965 it was discovered that changes in HRV could be used to detect fetal distress before any changes in heart rate would occur. In the 70’s doctors found that they could detect autonomic neuropathy in diabetic patients using HRV. And in 1977, it was discovered that HRV scores could be used to predict whether or not you would die from a having a heart attack.

Pretty cool, right?! But how can these beat-to-beat variations tell us all that?


A quick primer on the autonomic nervous system

First we need to address a common misperception: that the heart beats away at rest like a second hand or metronome. It does not, it’s responsive and therefore irregular. It’s responding to inputs like physical demands, emotional states, temperature, and general fitness levels. The nervous system senses and communicates and the heart responds. The general state or tone of the autonomic nervous system is reflected in these rhythms and variations.

The autonomic nervous system (ANS) has two branches, the sympathetic and parasympathetic. The ANS controls internal body processes such as the following:

  • Blood pressure
  • Heart and breathing rates
  • Body temperature
  • Digestion
  • Metabolism (thus affecting body weight)
  • The balance of water and electrolytes (such as sodium and calcium)
  • The production of body fluids (saliva, sweat, and tears)
  • Urination
  • Defecation
  • Sexual response

The sympathetic branch is the “fight or flight” instructor. It registers a stress and gets you ready to handle it. It speeds up some processes like heart rate and sweat. It makes fuel available for the brain by releasing glucose from the liver and puts a hold on any unnecessary spending (tissue repair and muscle building, immune system, energy storage, digestion) to keep all of your resources available for the approaching emergency (that it thinks you’re going to have).

The parasympathetic branch is the “rest and digest” facilitator. It restores you to a better version of yourself, adapted to handle whatever regular stressors you encounter, like exercise. It tells the body that it’s ok to spend time putting nutrients where they go and pick a fight with a cold you caught from your kid a few days back. It releases funds back to the projects your sympathetic branch put on hold.

When you are sympathetic dominant, it affects your HRV by making your resting heart beat more regular and mechanical, while a parasympathetic heart beat is more responsive and therefore less regular.

So whether you are sympathetically or parasympathetically driven can be measured at any given time using heart rate variability.

Now lets apply this to fitness and sports.

“For the athlete, intense training presents a large stressor to the body, invoking a strong sympathetic response to meet the increased metabolic demands.  Post-workout, as the sympathetic tone subsides, the parasympathetic system becomes facilitated and drives the rest and repair necessary to get things back to normal. Ideally, these two systems remain balanced in their efforts, each ramping up and down as needed.

If a technology existed that could assess this sympathetic/parasympathetic balance, coaches could gain an excellent understanding of an athlete’s physiological state and corresponding location on the fatigue-supercompensation continuum. Information like this could drive effective, evidence-based programming decisions. For example, adjustments in volume could be made on the fly specific to the recovery status of an athlete’s physiology.” – Joel Jameison 

Fortunately, this technology does exist and, as mentioned above, it’s called heart rate variability (HRV).


Supercompensation (aka how training makes us fitter)

Let’s talk a little more about the supercompensation continuum mentioned above. Supercompensation is a fun word describing how the body adapts to hormetic stressors, like exercise, to maintain homeostasis. Check out this video where Leibor explains it all using a graph that really hits it home.

This is why many high performance athletes use HRV monitoring to track their rest and recovery periods, pinpoint optimal training and competing times, and avoid overtraining. If you put too much volume and intensity in too frequently you will drive yourself into a state of overtraining.

Overtraining has many faces, but it’s a sucky place to be that turns your workouts against you. You become chronically sympathetic or parasympathetic. You either lose muscle mass or gain body fat. You don’t sleep well or you sleep way too much and you’re tired all the time. You may develop chronic tendinopathies or other random-opathies that won’t heal.

High intensity training is sympathetically driven. If you add that to a high stress job or relationship, you have a recipe for disaster. Training high intensity day in and day out, within the context of a normal stress load, can just as easily lead you into overtraining or burnout.

If you like to train more than 1-2 days per week, then having the options to train at lower intensities will boost your body’s recovery mechanisms while still providing stimulus and driving improvements. These are our AZT days. 1-2 days of high intensity each week is more than enough and it allows you to truly perform at high intensity on those VO2 max and threshold training days.

By tracking HRV daily, you can stay aware of excessive stress or insufficient recovery to make the most of the supercompensation curve.


Tracking HRV

This all sounds fancy and expensive, but the good news is that it’s not! You can download a free app and use your Basis heart rate monitor to take your own HRV measurements every day, first thing in the morning.

The instructions are simple:

  • Download the Elite HRV app
  • Pair it to your heart rate monitor
  • Go to sleep, wake up, pee, then grab your phone and go lie down
  • Turn on the app and take a reading when your heart rate stops dropping
  • Be perfectly still and don’t think about anything stressful or talk to anyone while taking a reading
  • Do this for 3 days in a row to establish your baseline reading
  • By day 4, your reading will be accurate

To keep it simple, if you get a green, you are good to train as planned. If you get a yellow, AZT as-is is fine but if it’s a high intensity day, lower the volume by 20% and keep the intensity dialed back as well. Just tell us you’re yellow, we get it. If it’s red, do Kinstretch and keep the intensity lower or take the day off.

By tracking HRV regularly, you can also see improvements in your fitness level as your score increases over time. Interestingly, one of the ways to see the biggest improvements in your HRV score is to increase your training frequency by doing more low intensity days, not by adding more high intensity work.


Do I have to track my HRV?

Of course not! Tracking HRV is recommended if

  • You train daily or close to
  • Compete
  • Need to manage your stress (stressed out, not sleeping, autoimmune, chronic injuries, at risk for heart attack)
  • Feel overtrained or under-recovered
  • Love data and are extremely curious

Tracking HRV is not recommended you

  • You tend to get neurotic about things
  • Don’t work out daily
  • Only have a few fleeting moments each week when you can make it into the gym and it will blow up your day and make you cry into your morning beverage or walk out into traffic if it comes up red or yellow

Whether or not you decide to use HRV as tool to enhance your training, hopefully the importance of balance has been well stated. The real magic happens when we recover. We’re all here and training because we know that it takes a stress to make us strong, but how well you respond is determined by how well you take care of yourself and drive recovery.


Happy recovering!