Recovery, explained
What your HRV actually means
Apple Watch vs Oura, and why your own trend wins. 44 seconds.
What does your HRV number actually mean? HRV is the tiny variation in time between heartbeats. Apple Watch measures SDNN. Oura measures RMSSD. Different math, so don't compare the numbers. Compare you with you: your seven-day line against your own range. Inside it, recovery is keeping up. A week below it? Often sleep, stress, alcohol, illness, or a hard block. One low night is just one night. That's why Coach never pushes you harder on HRV alone. Know someone who'd like Polaris? Share your invite link from Settings. Anything else? Just ask Coach.
In short
HRV is the tiny variation between heartbeats.
Your heart doesn't tick like a metronome. The small changes in time from one beat to the next are your heart rate variability. For you, higher usually means recovery is keeping up.
Apple Watch and Oura use different math.
Apple Watch reports SDNN from short readings taken while you're still. Oura reports RMSSD averaged through the night. Different measures, so the numbers don't compare, between devices or between people.
Compare you with you.
One night's number says little. Polaris shows your 7-day line against your own range from recent nights, and labels where the number came from: “Overnight HRV · Apple Watch (SDNN)”.
A week below your range is the signal.
It often means recovery is behind: sleep, stress, alcohol, illness or a hard training block. One low night is just one night, so Coach never pushes you harder on HRV alone.
Sources
- Plews et al., “Heart rate variability in elite triathletes…”, European Journal of Applied Physiology, 2012
- Plews et al., “Training adaptation and heart rate variability in elite endurance athletes”, Sports Medicine, 2013
- Altini & Plews, “What is behind changes in resting heart rate and heart rate variability?”, Sensors, 2021
General information, not medical advice. Bring health questions to your clinician.
Is this Alpha right for you?
Who it's for
You have a goal you're serious about, whether you're starting over or already training. You may have a full plan, a partial plan, or simply a clear place to start. You want help turning the whole picture into consistent action.
Who it's not
- People hunting a generic workout or meal generator
- People who want to collect data and leave it there
- Anyone who needs a human coach as the product
- Anyone using an Android device
Get the app on iPhone
No form and no invite code. Install Polaris from TestFlight on your iPhone, then sign up in the app with Sign in with Apple.
Is Alpha really free?
Yes. Free for as long as Alpha runs.
No card, no trial that turns into a bill. You can stop or delete your account any time.
Why free? You're early. Polaris is still being built, and your feedback shapes what it becomes. You get Coach first; we get honest answers. That's the whole deal.
What comes next: every Alpha member moves into the Beta. Polaris will be paid eventually, likely around $29.99 a month, with founding-member pricing for early members. You'll never be charged unless you choose to sign up.
Alpha requirement
Alpha runs on iPhone, with Apple Health syncing through the Polaris app.
- Apple Health on your iPhone
- TestFlight installed, then Polaris from our link
- Sign in with Apple in the app. No invite code
A few extra steps while we're in TestFlight. You sign up in the Polaris app, which walks you through Apple Health, and the app is required for this Alpha. Get the app on iPhone to get started.
Get the app
- Tap the button on your iPhone. It opens a page with three steps.
- Get TestFlight from the App Store, then come back to that page.
- Install Polaris in TestFlight, open it and sign in with Apple. Your account is made right there.
On a computer? Open this page on your iPhone, or tap the button and follow the three steps there.