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
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- People who want to collect data and leave it there
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