Channel

Metrics Explained

HRV, VO2 max, resting heart rate, readiness and strain: what each number means.

5min

Heart rate variability on your wearable: what the number means

HRV is the change in time between heartbeats. Here is how Oura, Whoop, Garmin, Fitbit and Apple Watch measure it, why their numbers can't be compared, how accurate they are, and how to read your own trend.

October 26, 2026

4min

Metrics Explained

Resting heart rate on your watch or ring: why devices disagree

Resting heart rate is one of the most reliable wearable numbers, but Oura, Apple Watch and Fitbit each define 'resting' differently. What it measures, how accurate it is, what raises it and when to see a doctor.

October 26, 2026