Heart Rate Variability – Common Misconceptions Debunked

By Jiri Kaloc

The term heart rate variability is being used more and more often. It can be a powerful tool to guide your training but only if you understand it well. Let’s debunk some of the most common misconceptions so you’re wiser than the rest.

Misconception #1: You need a chest strap to accurately measure HRV

The gold-standard method for measuring HRV is the electrocardiogram (ECG), which uses electrodes placed on your chest. Studies have shown that it aligns almost perfectly with photoplethysmography (PPG), which is the technology for tracking HRV with a phone camera or a smartwatch sensor.

So, for tracking HRV at rest, which is how it should be done most of the time, you can use an ECG, chest strap, a smartwatch or a phone camera and get accurate results. The problem with PPG tracking is that movement makes the measurement less accurate. A chest strap can certainly help with that. But then again, smartwatches that track overnight can solve this problem too as you don’t move while asleep for long stretches of time.

Misconception #2: Measuring overnight is best

There are two ways to get accurate and useful HRV measurements: overnight and in the morning. Measuring overnight is actually a bit harder because each sleep phase such as light sleep, deep sleep, and REM sleep has a different impact on your HRV. So, you need continuous monitoring all night, not just a few random spots during nighttime. And you need software to properly interpret the overnight data.

It’s also worth adding that evening exercise can impact part of your overnight HRV measurement. It will likely take some time for your HRV to go back to normal if you finished a hard ride 1-2 hours before going to bed. Your smartwatch may be fooled by this and think you need more rest than if you measured in the morning after fully resting.

To be fair, morning measurements also have drawbacks. You have to make sure to remain very still if you’re using the PPG technology. And you have to remember to do it first thing in the morning, as forgetting means a missed data point.

a group of cyclists
Measuring heart rate variability (HRV) can help you learn when to recover, when to train, and how to stay healthy. © Profimedia, ddp images

Misconception #3: Measuring HRV right before a ride is best

Heart rate variability can tell you if your body is ready for a high-intensity session or if you should opt for an easier ride. But measuring right before your ride is not going to give you more accurate results. In fact, it will give you completely useless data. Measuring during the day is problematic because of transitory stressors. Things such as physical activity, digestion, caffeine or even talking to friends or family can temporarily change your HRV. Measuring under the influence of a transitory stressor is not telling you how rested or exhausted your body is. This is the main reason why measuring in the morning or overnight is best.

Misconception #4: Resting heart rate is the same thing as HRV

They do have a lot in common. Resting heart rate (RHR) and heart rate variability both change when you’re under stress. But RHR is only influenced by large stressors and changes only very little. HRV is a much more sensitive and precise metric. A study compared how the two metrics change under different stressors and found that RHR changes only between 0,5–1%, and HRV changes by 5–10%. Both metrics have slightly different use and can be used in combination as we explained in the previous article.

Misconception #5: You should keep improving your HRV

There are ways you can improve your HRV as we discussed in the previous article. But it’s important to keep in mind that improvements are only possible by addressing a lifestyle problem.

  • If you are chronically stressed
  • If you are sleep deprived
  • If you have a poor diet
  • If you don’t exercise
  • If you often drink alcohol

Dealing with the abovementioned issues will allow you to improve your HRV. The HRV numbers you’ll be seeing after that will mostly depend on your genetics. HRV should be used as a continuous feedback loop for how you’re handling stress. HRV is not something like your power output, it’s not something you should try to or can continuously improve.

Misconception #6: HRV is only useful if you train hard and race

Training is not the only stressor in your life, no matter if you are a pro or just went for your first-ever ride yesterday. HRV is actually used by psychologists and therapists to capture how their clients are responding to stress and to help them better cope with it. HRV can help you notice you might be on the verge of getting sick. HRV reveals how well you’re dealing with the extra workload at your job, relationships problems or financial trouble. The longer you track HRV, the more uses you’ll be able to discover.