Guides · 5 min read

What is HRV, and why your own baseline matters

Heart rate variability explained simply: what it measures, why it moves, and why comparing it with your own normal beats comparing it with anyone else’s.

Heart rate variability — HRV — is the small variation in time between one heartbeat and the next. A heart beating at 60 beats a minute doesn’t tick exactly once a second; some gaps are a little longer, some a little shorter. HRV is a measure of that variation.

Why it moves

HRV reflects the balance of your autonomic nervous system — the part that runs things without you thinking about them. When you’re well rested, it tends to sit higher; hard training, short sleep, alcohol, stress and illness can all push it down for a while. That’s why recovery apps watch it closely: it often shifts before you consciously feel the change.

Why “good HRV” isn’t a number

HRV varies enormously between people. Age, genetics, fitness and even how a device measures it all change the number. Two healthy people can sit at very different values, and neither is “better”. Comparing your HRV with a chart of averages tells you very little.

What does tell you something is your HRV compared with your own recent HRV. A morning well below your usual is a signal; a value that would be low for someone else but is normal for you isn’t.

This is how RunPack works: your score is built from how far today sits from your own baseline, so 50 means exactly your normal.

Reading it well

Look at trends, not single days. One low morning is common; several in a row is worth noticing.
Measure the same way. Overnight readings from the same device are the most comparable.
Keep context. A late meal, a long flight or a hard race explain a lot.
Trust how you feel. If you feel fine and the number says otherwise, your body gets a vote.

A note on devices

Apple Watch writes HRV to Apple Health. Some other wearables measure HRV but don’t share it with Apple Health, so apps that read Health can’t use it. RunPack tells you when that’s the case and builds a recovery band from the signals it does have.

RunPack is not a medical device. HRV is a training signal, not a diagnosis.

Try it with your crewRunPack scores your recovery against your own normal and gives your training crew a card every morning. Free to start on iPhone.Coming soon to theApp Store