Tutorial Fitness Age and Vitality

Fitness Age, Vitality & Body Age

NOOP's Health tab turns your everyday strap data into three longevity-flavoured numbers: a Fitness Age, a Vitality score, and a Body Age. They're computed entirely on your device from published, peer-reviewed methods — and they're framed honestly as a fitness / wellness comparison, never a medical or "biological" age.

This guide explains what each number means, what feeds it, and how to move it.

Read this first: these are wellness comparisons, not diagnoses. NOOP is not a medical device. Every one of these numbers ships with a ± band and a plain disclaimer in the app for exactly this reason. Don't make health decisions from them — use them as a motivating trend.

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Fitness Age

What it is: how your cardiovascular fitness compares to an average healthy person — expressed as an age. A Fitness Age below your real age means you're fitter than a typical peer; above means there's room to improve.

How it's worked out (and why it's trustworthy): NOOP uses the Nes 2011 "HUNT" model — a large, peer-reviewed Norwegian study that estimates cardio fitness (VO₂max) from things you can measure without a treadmill test. The clever part: the headline Fitness Age needs only your age, sex, resting heart rate, and an activity level NOOP reconstructs from your measured weekly movement. (A body-size term that's in the underlying equation mathematically cancels out when comparing you to a reference peer, so you don't need to enter a waist measurement just to get the number.) An average-fitness person maps to their own chronological age by construction — so the scale is honest, not flattering.

What moves it: the two levers you control are resting heart rate (lower = fitter) and activity (more frequent, longer, more intense sessions). The reference peer sits at ~65 bpm resting HR and "moderately active a few times a week" — beat that and your Fitness Age drops below your real age.

The ± band: Fitness Age shows a ±5-year band and the line "a fitness comparison, not a biological age." Treat the trend over weeks as the signal, not a single day's number.

VO₂max (optional)

If you add a waist measurement in your profile, NOOP can also show an actual VO₂max estimate (ml/kg/min) from the same Nes waist-variant equation. It's optional — the Fitness Age works without it.

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Vitality & Body Age

What they are: Vitality is a transparent 0–100 wellness score; Body Age expresses the same thing as an age in years. They look at the wider picture than fitness alone.

How it's worked out: this is an independent implementation of the same published approach behind "healthspan"-style scores. Each wearable-measurable input is mapped to its published all-cause-mortality hazard ratio (from large cohorts and meta-analyses — UK Biobank, step- and activity-mortality pooled analyses, sleep-regularity and HRV cohorts), those are combined with a correction for the fact that the inputs overlap (fitness, resting HR and activity all move together), and the result is converted into a "years of aging" offset. Body Age = your real age + that offset, clamped to a sane range; Vitality maps the same offset onto 0–100 (≈50 means "right at your age").

What feeds it: any of — resting heart rate, VO₂max, average sleep, sleep consistency, nocturnal HRV (RMSSD), and daily steps. It uses whatever you have; the more inputs present, the sharper it is. It deliberately stays hidden until it has enough inputs rather than guessing from one number.

What moves it: the protective factors are the familiar ones, now quantified for you — a lower resting HR, better aerobic fitness, enough sleep, regular sleep timing, higher day-to-day HRV, and more daily steps. Because the model is conservative and clamped, you'll see steady nudges rather than wild swings.

Like Fitness Age, Vitality / Body Age carry a ± band and a hard "wellness trend, not a biological/clinical age" disclaimer. They're a mirror, not a verdict.

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Where to find them

Open the Health tab. The Fitness Age card sits near the top; Vitality / Body Age is just below it. Each recomputes as new data lands (Vitality is a weekly read; Fitness Age updates as your resting HR and activity trends move). If a card says it needs more data, keep wearing the strap — they fill in as your history grows, and importing your WHOOP history (or Apple Health / Health Connect data) gives them more to work with immediately.

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How to improve your numbers — practically

1. Build your aerobic base. Regular Zone-2 cardio lowers resting HR over weeks — the single biggest lever for both Fitness Age and Vitality.
2. Protect your sleep — amount and regularity. Vitality rewards consistent sleep timing, not just hours. A steady bed/wake schedule moves the needle.
3. Move more, most days. Daily steps and weekly active minutes both feed in.
4. Watch the trend, not the day. These are designed to drift slowly. A week-over-week improvement is real; a single-day jump is noise within the ± band.

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Everything here is computed on your device from your own data — nothing is uploaded, there's no account, and these numbers never leave your phone or Mac. They're a motivational lens on your own trends, not medical advice.

See also: Charge, Effort & Rest · Reading Your Sleep · The Science

NOOP is free and independent. If it's useful to you and you'd like to chip in, a one-off tip is optional and appreciated — see Donations.