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Heart Rate Variability – How to Track It

By Jiri Kaloc

Measuring heart rate variability (HRV) can help you learn when to recover, when to train, and how to stay healthy. There are many external and internal factors that influence HRV, which can make tracking it difficult. Let’s go over the best practices of tracking HRV as a cycling enthusiast.

HRV reveals how you deal with stress

HRV is a measurement that can tell you how your body is doing while trying to maintain a state of balance. It can reveal how well your body will respond to an acute stressor within the following 24-48 hours. Here are a few examples of acute stressors:

  • An intense workout
  • Drinking too much alcohol
  • A long flight
  • A menstrual cycle
  • An illness
  • A very bad night of sleep

But more interestingly, HRV can also tell you how you adapt to long-term changes in your lifestyle over weeks and months:

  • Changes in training load and intensity
  • Changes in nutrition
  • Changes in sleeping habits
  • Changes in work-life balance
Tracking HRV can be confusing at first, you see values jumping up and down from day to day and even more so hour to hour.

Measure in the morning or overnight

The problem with measuring HRV is that so many things influence it from one moment to another. If you want a number that truly captures levels of your physiological stress consistently over days, months, and years, you need to avoid measuring when transitory stressors are impacting you. Here are examples of common transitory stressors:

  • Physical activity
  • Digestion
  • Caffeine
  • Talking to friends or family

As you can see, it’s nearly impossible to avoid these stressors during the day. That’s why most research on heart rate variability recommends measuring in the morning or overnight.

Morning: You should measure as soon after waking up as possible, ideally when still in bed. The measurement should last between one and two minutes to give reliable results.

Overnight: You can achieve this by wearing a device that can continuously and precisely measure your heart rate. Wear it when you go to sleep and during the whole night to get reliable results.

What devices track HRV?

The gold-standard way to measure HRV is the electrocardiogram (ECG). You probably saw it if you ever had your heart checked at the emergency room or at a cardiologist. You get electrodes attached to your chest and the machine displays that typical graph depicting heartbeat that you see in Hollywood movies.

Thankfully, in recent years, a number of wearable non-medical devices have emerged that are precise enough to track HRV. A recent study compared several popular devices to an ECG. Here is how they stacked up:

  • WHOOP 3.0 – accuracy 99%
  • Somfit – accuracy 69%
  • Apple Watch S6 – accuracy 67%
  • Polar Vantage V – accuracy 65%
  • Oura Ring Generation 2 – accuracy 63%

Overall, the accuracy is very good considering that these devices can comfortably be worn 24-hours a day. Plus, the devices in this study are already outdated. New generations have better sensors and more sophisticated software. Other companies like Garmin are introducing HRV as well. It’s clear that tracking HRV is going mainstream and this is the way most people will get access to it.

Now that you know how to measure and track your HRV, it’s time to dig deeper into how to interpret your HRV and how to use it in your training. The next article will be all about that.

Next up in Heart Rate Variability series