Heart Rate Zones

SparkyFitness splits heart rate into five zones. The same zones are used everywhere: the time-in-zone chart on a workout, the training load on Exercise Statistics, and the heart rate ranges suggested when you plan a run.

Where to set them

• Mobile: Settings → Heart Rate Zones.
• Web: Settings → Profile & Account → Heart Rate Zones.

The screen shows your five zones with their bpm ranges, and where your max heart rate comes from:

Shown as	Meaning
You set it	You entered a max heart rate.
From your date of birth	Worked out from your age with the Nes formula, 211 − 0.64 × age.
From the highest heart rate in the workout	No date of birth and no max set; used while splitting a single workout.
A typical value	Nothing to go on, so 190 bpm. Add your date of birth or set your own.

On iPhone with iOS 27 or later, Use Apple Health zones reads the heart rate zones from Apple Health and fills them in as custom zones. It does not change your max heart rate. If resting heart rate is empty, it fills that from Apple Health too. Nothing is stored until you tap Save, and past workouts are not recalculated. The button is hidden on older iOS versions and on Android, because Apple only shares those zones with apps from iOS 27, and not as a normal Health sample.

A workout that Apple Health already split into zones keeps Apple's time in each zone, instead of being worked out again from your settings. That covers a workout recorded in the Fitness app, a run recorded on Apple Watch, a workout recorded in Sparky on the watch, and a phone GPS recording whose watch workout was saved. The chart matches the Fitness app, including time below the first boundary, which Apple counts as zone 1. Those workouts say the zones were set by the device. This needs iOS 27 or watchOS 27. Anything Apple did not split still uses your settings. Past workouts are not rewritten.

Max heart rate must be 100 to 250 bpm and resting heart rate 25 to 150 bpm. Leave max empty to go back to the date of birth estimate. Reset to default clears everything on the screen.

Zone methods

Method	Zone 1 to 5 start at
% of max heart rate (default)	50, 60, 70, 80 and 90% of max heart rate.
Heart rate reserve (Karvonen)	Resting heart rate + 50, 60, 70, 80 and 90% of the gap between resting and max. Needs a resting heart rate.
Custom zones	The five bpm values you enter. Each zone must start above the one before it.

If you pick a method that is missing what it needs (heart rate reserve with no resting heart rate), zones are shown as % of max heart rate and the screen says so.

Time below zone 1 is not counted in any zone.

Which age formula is used

Everything uses the Nes formula (211 − 0.64 × age). It is the formula stored zones have always used, so zones for people who change nothing stay exactly as they were. Two places used other formulas before and now follow it: training load (220 − age) and suggested heart rate ranges for a planned run (Tanaka, 208 − 0.7 × age). Training load and suggested ranges can shift by a few bpm or a few load points for people who have not set their own max heart rate.

Suggested ranges for a planned run now come straight from your zones: warm-up and cool-down are zone 1, easy is zone 2 and fast is zone 4.

Showing five zones or four tiers

Under Show in Heart Rate Zones settings you can choose 5 zones (the default) or 4 tiers. Four tiers are Light (zones 1 and 2 together), Moderate (zone 3), Vigorous (zone 4) and Peak (zone 5). It only changes what you see in the settings list and in the Heart Rate report. Your zones are still worked out, stored and used for training load and suggested ranges as five, and past workouts are not changed.

The Heart Rate report

The Heart Rate report (web: Reports > Heart Rate; mobile: Reports > Heart Rate) shows your own zones with the bpm range of each (Zone 1 to Zone 5, or the four tiers if you chose them), the same ranges as in Settings. Lines on the heart rate charts change color at the start of each zone. Under the zone list the report says where the zones come from (your method and max heart rate, and whether that came from you, your date of birth or a typical value) and links to Heart Rate Zones in Settings. Until your zones load, or if you have set nothing and have no date of birth, it shows the typical zones (percent of a 190 bpm max) and says so.

The mobile report is built from daily summaries (resting heart rate, recovery), so it lists zone ranges only and does not count time in each zone. Time in each zone is shown for each workout on the web report. It uses the zones stored with that workout; if a workout has none, it is worked out from the workout's heart rate readings with your zones as they are now.

What changing zones does to past workouts

Changing your zones does not rewrite past workouts. Time in zone is worked out when a workout is recorded or synced and stored with the zone boundaries and the method used, so history never shifts under you. New settings apply to:

• workouts you record or sync from now on;
• training load (which is calculated on demand from your current zones);
• suggested ranges for planned runs.

Zone charts say which method the workout's zones were worked out with ("Zones: Heart rate reserve…"). Workouts from a Garmin or other device that supplies its own zones say the zones were set by the device. Workouts stored before methods were recorded show no method.

For developers

• Shared logic: shared/src/utils/heartRateZones.ts. floorsFromAppleHeartRateZones turns Apple's five preferred zones into custom floors (zone 1 with no lower bound starts at 30 bpm; any other count is ignored). The phone reads them with modules/apple-heart-zones on iOS 27. bucketsFromAppleWorkoutZones turns a finished workout's heart-rate zone group into stored rows (zone_method device) and keeps time below the first boundary as zone 1; the server uses that instead of computeTimeInZones when a sync or a watch post includes it. resolveHeartRateZones turns settings and date of birth into the five zones; heartRateZoneRange(resolved, zone) returns the bpm range of zone N (the top zone ends at max heart rate); computeTimeInZones buckets a heart rate series.
• Reports: web components/HeartRateZoneLegend.tsx, hooks/Settings/useHeartRateZones.ts (useResolvedHeartRateZones) and utils/heartRateZoneBands.ts; mobile components/reports/HeartRateZoneRanges.tsx. All of them take zones from resolveHeartRateZones via the API, with defaultHeartRateZones, heartRateZoneBands and heartRateDisplayBands (the five zones or four tiers, with colors) from shared. The choice is hr_zone_display_count on user_preferences (4 or 5, default 5), sent as display_zones by the API. Do not add fixed bpm tiers.
• API: GET / PUT /api/v2/heart-rate-zones (owner-only; contract in shared/src/schemas/api/HeartRateZones.api.zod.ts).
• Storage: max_heart_rate, resting_heart_rate, hr_zone_method, hr_zone_custom_floors on user_preferences; zone_method on exercise_entry_hr_zones.