In one sentence
The fastest your heart can beat, which you record once in your body measurements, and the four bands of effort that every training session is read against as a share of it.
Why it matters
Heart-rate zones only mean something relative to your own maximum. A session at 150 beats a minute is easy for one person and near the limit for another, and the difference is the maximum. Everything on VT's activity sheet that reads effort from heart rate, the time in each zone, the mix of fuel the body was likely burning, and the Cardio Load figures, starts from this one number, so a wrong maximum skews all of them in the same direction.
Where the number comes from
The best source is a measurement: the highest rate your device recorded during an all-out effort at the end of a hard session, repeated on more than one occasion. A formula is a fallback. The familiar 220 minus age was never derived from a study designed for the purpose; when Tanaka and colleagues pooled the published measurements and tested the result in their own laboratory, the line 208 − 0.7 × age fitted better, and 220 minus age under-read the maximum in older adults (Tanaka 2001). Either formula has a spread of many beats around it for an individual, which is why a measured value wins.
What moves it
Almost nothing in the short term; it is a property of the heart, not of fitness. Across populations it falls slowly with age, which the formulas encode. Heat, dehydration and fatigue lower the rate you can reach on a day without changing the true maximum, and a measured maximum from a sick or exhausted session is a floor, not the answer.
How to record it well
Enter a measured value if you have one from a maximal effort; if not, use the Tanaka formula and replace it the first time your device records something higher. Keep it current: a maximum recorded years ago is out of date.
How Vitality Tracker uses it
Stored with your body measurements and used by the activity sheet to place each minute of a session in one of four zones, to read the session's intensity and to estimate the share of fat and carbohydrate burned. Activity Units and the daily Cardio Load figures do not use it: they take a maximum from your age (208 − 0.7 × age), raised a little when your watch sees you hold a higher rate. The founder's activity sheet of 28 October works against a recorded maximum of 184: a minute at 165 beats is 90 percent of it, in the Peak zone.
How far to trust the number
Self-reported; its quality is yours. A measured maximum is accurate to a beat or two; a formula is an estimate with a wide spread.
Sources
- Tanaka H, Monahan KD, Seals DR. Age-predicted maximal heart rate revisited. J Am Coll Cardiol 2001;37:153–6. doi:10.1016/s0735-1097(00)01054-801054-8>)
- Vitality Tracker, What VT measures (catalogue of 15 October 2026).