Five zones, from easy to all-out, computed from your personal max and resting heart rate. Effort feels different day to day; heart rate doesn't lie. Every zone change is spoken through your AirPods — scroll to move through them.
Everything easy lives here — warm-ups, cool-downs, recovery days. Zone 1 has no floor, the screen goes a calm blue, and FitZones mostly keeps quiet: this zone is supposed to feel like nothing.
The base-building zone — the effort where you could still hold a conversation. It's where the aerobic engine gets built: more mitochondria, better fat metabolism, a lower heart rate at every pace. Elite endurance athletes do most of their training here.
The problem: zone 2 feels too easy. Without feedback, almost everyone drifts into zone 3 and turns an easy day into a junk-mileage day. FitZones says so the moment you drift, before you cross the line.
Comfortably hard. Yellow means you're working — great for tempo miles, but a warning sign on a day that was supposed to be easy.
Orange is interval territory. Did you actually get up to the zone, or just feel like you did? FitZones announces the moment you arrive, so you spend your hard minutes actually training hard.
All-out, and the screen goes red to match. Short visits, fully earned, counted to the second in your summary.
This is where VO₂max gets built — one of the best-studied markers of cardiovascular fitness, and one that large studies consistently link with living longer.
AirPods Pro 3 and Powerbeats Pro 2 carry built-in heart rate sensors, and the ear is a genuinely good place to read from: blood flow is strong, and earbuds sit still at a sprint while a watch shifts and bounces on your wrist.
AirPods Pro 3 and Powerbeats Pro 2 measure heart rate from your ear. FitZones starts a real workout session on your iPhone, which tells them to begin streaming.
Outdoor or indoor run or walk, or a hike. Outdoor workouts add GPS distance, pace, and a route map.
FitZones speaks when your zone changes, warns you as you approach a boundary, and reads out your stats at the interval you choose. Music ducks for a moment, then comes right back.
When you're done, FitZones shows the run the way a coach would read it: duration, distance, calories, average and max heart rate, the full heart rate curve, and exactly how long you spent in each zone.
Everything spoken is a toggle. Zone changes, the approaching-zone warning and how close it triggers, and periodic stats where you pick the interval and the exact parts: elapsed time, average heart rate and zone, distance, pace.
There's even a test announcement button, so you can hear how it sounds before you're a mile from home.
Pick Heart Rate Reserve (the Karvonen method — the same one Apple Watch uses) or a flat percent of max. Max heart rate is estimated from your age and sex with the Tanaka or Gulati formula, or set it manually if you know your real number.
Resting heart rate syncs from Apple Health with one tap, so your zones adapt as your fitness improves.
Voice guidance is only useful if it isn't annoying. Most of the engineering in FitZones went into knowing when not to speak.
A new zone has to hold for several seconds before it's announced, with hysteresis on top. Hovering at a boundary won't trigger a "zone 3, zone 2, zone 3" loop in your ear.
Announcements duck your audio and release it as soon as they finish. Podcasts, playlists, and audiobooks carry on uninterrupted.
Lock your phone, switch apps, keep your music going. Announcements and tracking continue for the whole workout.
Outdoor and indoor runs and walks, plus hikes. Outdoor workouts get GPS distance, pace, and a route map; indoor ones focus on heart rate.
Workouts save to Apple Health with route and calories. Already recording on a Watch? Flip one toggle and FitZones keeps its own history without double-counting.
No account, no subscription, no ads, no analytics. Your workout data lives on your iPhone and in Apple Health, nowhere else.
