What is Resting Heart Rate
We use RHR across many Wellhero metrics. We are updating how we calculate it. Before we explain the new method, let’s be clear about how and why we use RHR.
Resting heart rate (RHR) is a key marker of how your heart works. It shows how fast your heart beats when your body is calm. At rest your organs do not need extra blood flow like they do during exercise, movement, digestion, or stress.
When stroke volume is higher, the heart needs fewer beats to deliver the same blood. Stroke volume does not change much from day to day in most people, so we can treat it as relatively stable. That means the body adjusts resting blood supply mainly by changing heart rate. Hormones and the autonomic nervous system push the rate up or down. A higher RHR at rest can signal higher arousal or stress. A lower RHR often reflects efficient heart function and good recovery.
What Can RHR Tell You?
Recovery
We use RHR as a core part of our recovery analysis. If your body has recovered from stress, resting heart rate goes down. Even small changes can signal progress. Athletes know this from experience: right after an intense workout, your heart rate stays elevated, even if you sit still. Ten minutes later it’s lower, half an hour later it drops more, and hours later it gets closer to normal.
The drop depends on workout intensity and duration. After a marathon, runners often have elevated RHR for several days. For me, it takes about three days for my RHR to return to baseline after a full marathon. After a half marathon, one good night’s sleep is usually enough.
Cardio Load (Strain or Exertion)
We also plan to expand training analysis in Wellhero with daily cardio load. Most apps calculate this using TRIMP (training impulse). It’s not magic, but to do it right we need to know your Cardio Reserve: the difference between your maximum heart rate and your resting heart rate.
How to Measure Resting Heart Rate
The best time to measure resting heart rate is right after waking up, in a calm setting. In reality, though, most people don’t wake up stress-free. Alarms, rushing thoughts, and daily worries can skew the results. That’s why we built a flexible approach in Wellhero.
Here’s how we calculate RHR:
- Best case: you sleep with Apple Watch and have a sleep schedule set up.
During sleep, when the body is most relaxed, the watch records heart rate frequently. For example, after a cycling race I slept 9.5 hours, and my watch logged 134 heart rate samples. For comparison, blood oxygen was measured 16 times, and HRV only twice. - You don’t sleep with the watch, but you take an HRV measurement right after waking up.
If you tag it as “Morning awake,” we use that value. This method works well, especially if done before coffee or any activity. - You skip mornings, but take HRV readings during the day.
That’s fine too. We take the lowest heart rate recorded during your HRV test, assuming you measure in a calm state. It’s not perfect, but it’s better than nothing. - You don’t measure HRV at all, but you use Apple Watch and sync with Apple Health.
In that case, we rely on Apple’s automatic HRV readings. The watch detects calm moments during the day and records HRV, and heart rate. We import and analyze those values to track your RHR.
The Hidden Pitfalls of Measuring RHR During Sleep
When you sleep with Apple Watch, you may get hundreds of heart rate readings. The problem: they are not the same. Even though the body is resting, the numbers vary.
For a long time, we used the lowest heart rate during sleep as RHR. But after analyzing hundreds of thousands of sleep records, we found a better way. Instead of taking the single minimum, we now use the 5th percentile value (the lowest 5%).
This reduces random measurement errors and gives a more stable, reliable result. Most importantly, it doesn’t change the overall trend of your data.
We will recalculate and automatically update all historical values in the app. That means new RHR numbers for each sleep session, refreshed baselines, and updated recovery indexes. Don’t expect big shifts as your metrics will remain consistent, just more accurate.
How the Numbers Will Change
Switching from “minimum value” to “5th percentile” slightly adjusts RHR, but in most cases the difference is small.
Change in resting heart rate (bpm) → % of cases
- 0 bpm (no change) → 20%
- +1 bpm → 29.5%
- +2 bpm → 20.2%
- +3 bpm → 12.3%
- +4 bpm → 7.9%
- +5 bpm or more → 10.1%
In other words, the new method smooths out noise without drastically altering your baseline.
Why Not Just Use Apple’s Resting Heart Rate?
Apple Watch can calculate and save resting heart rate directly into Apple Health. Sounds convenient, but there are problems:
- It’s a black box. We don’t know when Apple Watch takes the measurement, how often, or even the exact timing. That means we can’t explain to users how it works or why they should trust it.
- It doesn’t match other trackers. If you also train with devices like Garmin, Apple’s RHR will often read higher. In contrast, the 5th percentile method produces values that align much more closely across different platforms.
Real-World Example
To see why we switched to the 5th percentile method, here’s a personal test. I slept with two watches at the same time:
- Apple Watch RHR: 56 bpm
- Garmin Fenix 6 Pro RHR: 49 bpm
- Wellhero (5th percentile of sleep): 49 bpm
As you can see, Apple Watch reported a higher value. Garmin and Wellhero matched. This shows why the 5th percentile method gives more consistent results across different devices.
We’re Not Removing Minimum Sleep Heart Rate
You will still have access to the minimum heart rate during sleep in your sleep analytics. Soon, we’ll also add a new metric: heart rate dip: the decrease in heart rate during sleep, especially in non-REM stages. This will give you an even clearer picture of your recovery.
Thank you for staying with us! 🌸
