HRV and readiness, explained simply
Heart rate variability has gone from lab measure to lock-screen widget. Used well, it is a useful nudge about recovery. Used badly, it is a number that makes you anxious. Here is how to read it.
The short version
- HRV is only meaningful against your own baseline from the same device.
- Several low days together matter; one low day usually does not.
- A good readiness score combines HRV with sleep, resting heart rate, how you feel and training load, and shows which one moved.
- Use readiness to rearrange hard and easy days, not as permission to stop training.
What HRV actually measures
Your heart does not beat like a metronome. The time between beats changes slightly from one beat to the next, and that variation is heart rate variability. It mostly reflects the balance of your nervous system: when you are relaxed and well recovered, the gaps tend to vary more; when you are stressed, ill, short on sleep or tired from training, they tend to vary less.
Most watches and rings report a measure called RMSSD in milliseconds, usually taken overnight or first thing in the morning. Different devices measure differently, so compare yourself only with readings from the same device.
Your baseline is the point
There is no good HRV number. Healthy adults range from the teens to well over 100 ms, depending on age, genetics and fitness. Comparing yours with a friend’s tells you nothing.
What matters is how today compares with your own normal. A common approach is to look at a rolling average of the last week against your longer-term baseline over the last month or two. One low reading means little: HRV moves day to day with a late meal, a drink, a hot room or a bad night. Several days in a row below your normal, especially alongside a raised resting heart rate, is a stronger signal.
What a readiness score adds
A readiness score combines HRV with other signals so that one noisy number does not decide your day. Typical inputs are:
- Sleep: how long and how well you slept last night and over recent nights.
- Resting heart rate, compared with your normal.
- How you feel: soreness, energy, mood and stress.
- Recent training load: how much hard work you have done lately compared with what you are used to.
The most useful scores show which inputs moved the number, so you can tell “slept badly” apart from “legs are wrecked from Monday”.
How to use it day to day
| Readiness | What to do |
|---|---|
| High, and you feel good | Do the planned hard session, or push a little. |
| Normal | Train as planned. |
| Low for one day | Train, but keep the hard part shorter, or swap it with an easy day later in the week. |
| Low for several days | Take an easy or rest day, prioritise sleep and food, and look for the cause. |
Readiness should change the shape of your week, not stop you training. And if you feel unwell, rest regardless of what any score says.
Things that lower HRV (that are not training)
- Alcohol, even a couple of drinks, especially close to bed.
- Short or broken sleep, and late heavy meals.
- Illness coming on: a sudden drop can show up before symptoms do.
- Travel, heat, dehydration and work or life stress.
Recovery & Readiness Score from Sleep, HRV and Training
A daily 0–100 readiness score from sleep, HRV, resting heart rate, soreness, energy and training load, with reasons. Reads Apple Health and Health Connect.
See how Sets & Splits does itQuestions
What is a good HRV?
There is no universal good HRV. It varies widely with age, genetics and fitness. Compare today’s reading with your own recent average from the same device.
Do I need a smartwatch for a readiness score?
No. Sleep, soreness and energy can be entered by hand. A watch or ring adds HRV and resting heart rate automatically.
Should I skip training when my readiness is low?
Not necessarily. For one low day, a shorter or easier session usually works. Several low days in a row are a better reason for an easy or rest day.
General training information, not medical advice. If you have a health condition, an injury or symptoms, talk to a doctor or a qualified professional.