How (not) to use heart rate

Heart rate readings do not have a universal meaning like MPH. The significance of a given heart rate depends on the physiology of the person, similar to RPM.

How (not) to use heart rate
Photo by Shuaib Khokhar / Unsplash

While watching a Formula 2 race last weekend, I noticed that some of the drivers were broadcasting their heart rates. Then I read that the FIA thinks it has to be careful with the data, which is absurd. On its own, a BPM reading means nothing.

Heart rate is like the RPM of an engine. No one ever says, "Look at that car going 6,000 rpm!" Why? The significance of RPM depends on the vehicle. It does not directly reflect speed.

Heart rate is like engine speed, but we're all driving different cars. The relevance of the reading depends on its relationship to a benchmark; that's redline for engines and thresholds for heart rate. So whenever you hear a comment like, "His heart rate was X!" you can smile and ignore it.

Here's a checklist for meaningful heart rate data:

  1. Ignore formulas. Formulas like "220 minus your age" don't work. They describe populations, but rarely individuals. I've worked with athletes with maximum heart rates from 160 to 212. (The 212 was 45 years old.)
  2. Don't trust estimates. Unless a person has spent thousands of hours comparing their perceived exertion to a proper reading, estimates are just guesses. And even with lots of experience, estimates are still questionable.
  3. Record electrical activity with a chest strap. Wrist-based, optical monitors attempt to read blood flow below the skin, not electrical activity of the heart. They're an indirect measurement and horribly imprecise.
  4. Find a personally relevant benchmark. There are three to choose from:
    1. Aerobic threshold (most important, but hardest to measure)
    2. Maximum heart rate (interesting, but little use outside of cocktail parties)
    3. Anaerobic threshold (most common, most practical to measure)
  5. Compare readings to your benchmark as a percentage. This is the only way that heart rate readings can be compared to other people. "Joe's at 160!" means nothing. But "Joe's at 109% of anaerobic threshold!" means he's in The Pain Cave.