Your wearable heart data: VO2max, HRV and resting heart rate

If you wear a watch or a ring, you already carry some of the most useful heart information there is, gathered day after day in real life rather than in a five-minute snapshot. Three numbers stand out, and together they say a lot.

VO2max reflects your cardio-respiratory fitness, how well your body takes in and uses oxygen, and fitness measured this way is one of the strongest single predictors of long-term health there is. The figure on your watch, though, is an estimate worked out from your heart rate and your pace, not a direct measurement. It is good for following your own trend over months, but it is not a precise reading. For an accurate VO2max you need a lab test, on a treadmill or bike with a mask that measures the air you breathe: the watch gives you the direction, the lab gives you the number. A low figure is a reason to build aerobic fitness, not a verdict, because it responds to training at any age.

Resting heart rate is how fast your heart beats when you are still. Lower is generally better, a sign of an efficient, well-conditioned heart, though what matters most is your own trend over time. A resting rate creeping up over weeks can be an early flag of overtraining, illness or stress.

Heart rate variability, or HRV, measures the tiny variation in time between beats. Higher variability tends to reflect a well-recovered, adaptable nervous system; a sustained drop often tracks with stress, poor sleep, alcohol or illness before you feel it.

None of these is a diagnosis, and the numbers come with caveats. Accuracy varies between devices and with how the watch is worn, the wrist sensor struggles most during hard or jerky exercise, and a loose strap, cold hands or a tattoo can throw a reading. Sleep stages are an approximation, and any blood-oxygen or single-lead ECG features are screening-grade rather than a clinical test. So they are best read as your own trends over time rather than as exact figures or against anyone else. Read that way and brought to a heart review, they add real context, showing how your heart behaves across a normal week rather than in the clinic alone.

You can upload your data with your online questionnaire, or bring it to a visit. We do not sell wearables and have no stake in them, so we will look at what yours show alongside your bloods and your history, and tell you what it adds and where it stops.

Ready to start? Choose the check that fits your question and tell us a little about yourself. A doctor reviews it, arranges what you need, and explains what it means. Most of it is done online, with the clinic there if you would rather be seen.