Metric

Heart Rate Variability

What your HRV number means, what moves it, and how to read it without overreacting to a single morning.

Heart rate variability is one of the most watched and least understood numbers on a wearable. It swings with sleep, stress, alcohol, illness, and training, which makes a single reading hard to interpret and a trend worth watching. Here's what the research says it means, what's been shown to move it, and where the science still isn't settled.

The benchmark
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.

See how you compare
Example result
Woman · 40 · 34 ms
around the median for your age
from 84,772 adults
Research Desk · live file
See the full HRV evidence file
Every claim rated Established, Emerging, Uncertain, Insufficient, or Unsupported, with a research log reviewed against new studies on a rolling basis.
Open the Research Desk →
More on Heart Rate Variability
Why Did My HRV Suddenly Drop?
A single low morning is almost always a normal response to something from the day before, not a warning about your heart.
What Is a Good HRV? It Depends More Than You Think
A number that looks low on one person's wrist can be completely normal on another's.
Does a Low HRV Reading Mean You Are Anxious?
Research confirms a real link between reduced HRV and psychological stress, but the number cannot tell you which stressor drove it.
How Wearables Actually Measure HRV
The sensor on your wrist and the strap across your chest are doing fundamentally different things.
Other metrics
Heart Rate Variability Resting Heart Rate Sleep VO2 Max