Heart rate and rhythm metrics

Vita reads resting heart rate, heart rate variability, daily heart-rate range, walking average heart rate, one-minute heart rate recovery and blood oxygen from Apple Health — resting heart rate and HRV being the core inputs to recovery, stress and Body Age.

Resting heart ratebpm

Field: resting_heart_rate

What it measures: A single daily estimate the Apple Watch derives from long still periods (usually including sleep) — not the lowest heart rate of the day.
What Vita does with it: Recovery (25%), stress (25%) and Body Age (capped at ±3 years).
Easily misread: Caffeine, alcohol, room temperature, infection and altitude all move it. A single elevated day means little; a sustained shift against your own baseline does.

Heart rate variability (HRV)ms

Field: heart_rate_variability

What it measures: How much the interval between heartbeats varies. Apple reports **SDNN** (the standard deviation of intervals), typically sampled during sleep, once per day.
What Vita does with it: Recovery (35%), stress (60% — its largest term) and Body Age (±3 years).
Easily misread: 🚨 **SDNN is not the same number as WHOOP's rMSSD** — the two are not directly comparable. Between-person variation is enormous (two equally healthy people can differ severalfold), so it is only meaningful against yourself.

Average / min / max heart ratebpm

Field: heart_rate_avg

What it measures: The mean, minimum and maximum of the day's heart-rate samples. The Apple Watch samples roughly every 5 minutes at rest, and far more often during workouts.
What Vita does with it: Displayed as a trend in the Health tab; not an input to any score.

Walking heart rate averagebpm

Field: walking_heart_rate_average

What it measures: Average heart rate during steady walking — not running or climbing — which reflects the cardiovascular cost of ordinary activity better than resting heart rate does.
What Vita does with it: Displayed as a trend in the Health tab.
Easily misread: A gradual fall at the same pace usually signals improving fitness, but pace itself moves it — so read the trend alongside any change in walking habits.

One-minute heart rate recoverybpm

Field: heart_rate_recovery_one_minute

What it measures: How far heart rate falls in the first minute after exercise ends. A larger drop generally indicates more effective autonomic recovery.
What Vita does with it: Displayed as a trend in the Health tab.
Easily misread: Only produced when the Apple Watch records a workout of sufficient intensity, so the data is often sparse.

Blood oxygen saturation%

Field: blood_oxygen_saturation

What it measures: The percentage of haemoglobin in the blood carrying oxygen, estimated by the optical sensor on the back of the watch.
What Vita does with it: Health-tab trend, and one of the readings in the widget's Vitals template.
Easily misread: Strap tightness, skin tone, tattoos, cold and arm position all affect it, so single readings are noisy. ⚠️ The feature has been disabled on some Apple Watch models in some regions due to a patent dispute, so the data may simply be absent.

Blood pressure (systolic / diastolic)mmHg

Field: blood_pressure_systolic

What it measures: Written into Apple Health by an external cuff, or entered by hand. The Apple Watch does **not** measure blood pressure.
What Vita does with it: Displayed, and used as context when interpreting an uploaded lab report; not an input to any score.
Easily misread: 🚨 A clinical measure. Vita displays it and does not interpret or grade it — take questions about blood pressure to a clinician.

Limitations

For users who also wear a WHOOP, an overlapping metric (resting heart rate, HRV) takes its values from a single source for the whole window — mixing two vendors' algorithms would poison the baseline.
All heart metrics are shown by day in the Health tab; how complete the data is depends on the Apple Watch's sampling.

References

Apple. HealthKit — HKQuantityTypeIdentifier reference. Apple Developer Documentation, accessed 2026.
What it supports：The official definition, unit and aggregation style of each metric — the source for how every field on this page is described.
Shaffer F, Ginsberg JP. An Overview of Heart Rate Variability Metrics and Norms. Frontiers in Public Health. 2017;5:258.
What it supports：How HRV metrics differ (SDNN and rMSSD are not the same number) and their normative ranges.
Jensen MT, Suadicani P, Hein HO, Gyntelberg F. Elevated resting heart rate, physical fitness and all-cause mortality: a 16-year follow-up in the Copenhagen Male Study. Heart. 2013;99(12):882-7.
What it supports：Elevated resting heart rate independently tracks mortality after adjusting for fitness.

Every metric on this page is a reference index for observing your own trends. It is not medical advice and cannot replace a professional diagnosis. If you have health concerns, consult a qualified clinician.

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