We interpret · You decide

Your wearable gives you the number. We read the research on what it means.

HRV, resting heart rate, sleep, VO2 max. What's normal for someone your age, what moves each one, and where the science is still unsettled.

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KnowYourPrime We read the research
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Heart Rate Variability
HRV by Age: What's Normal for Men and Women
Where your number sits for your age and sex, and why the ranges online disagree with each other.
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84,772 adults in the reference dataset behind the numbers
The metrics

Four numbers, read honestly

Clear, sourced, and written to be useful

Heart Rate Variability Resting Heart Rate Sleep VO2 Max
Live evidence files

The Research Desk

Every claim rated, reviewed on a rolling basis

HRV Research Desk RHR Research Desk Sleep Research Desk VO2 Max Research Desk
Heart Rate Variability
HRV by Age: What's Normal?
Where your number sits for your age and sex, and why the ranges you find online disagree with each other.
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Resting Heart Rate
Resting Heart Rate by Age
The normal ranges by age and sex, and what a high or low reading does and doesn't tell you.
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VO2 Max
VO2 Max by Age: What's Good?
What counts as a good VO2 max for your age, and how much to trust your watch's estimate.
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Sleep
Sleep Score Explained
What goes into a sleep score, why a long night can still score badly, and what it's really tracking.
Read & use the tool
How we read the data
How We Interpret Wearable Data
Why trends beat single days, why your baseline matters more than any average, and how we judge the evidence.
Our approach

Most of what's written about these numbers is either vague or trying to sell you something. I read the actual studies and write down what they say, including the parts that aren't settled. You make up your own mind from there.

Kate Maren, Editor
How we interpret
Three things we hold to
  • Independent. We don't sell a device, a supplement, or a program.
  • Evidence-led. Every claim traces back to a named study.
  • Interpretation only. We explain the research. We never tell you what to do.
Read our approach