In The Zone Training

Train by heart rate zone, not guesswork. Prop your phone on the treadmill and read your effort by colour alone.

Train by heart rate, not guesswork.

Effort is easy to misjudge. You set out for an easy run and finish it tired; you plan a hard session and coast. In The Zone shows which of five training zones you're actually working in, live, so you can tell the difference while it still matters.

A GLANCE, NOT A STARE Prop your phone on the treadmill and the whole screen becomes your zone's colour. Green means easy, red means you're deep in it. You can read your effort out of the corner of your eye, without breaking stride to squint at a number.

YOUR WATCH DOES THE WORK Live heart rate comes from an Apple Watch workout, so the readings are immediate rather than minutes stale. Set a target zone and your watch taps your wrist when you drift out of it — one pattern for working too hard, another for easing off. You can hold a zone without looking at anything at all.

BUILT FOR INDOORS AS WELL AS OUT Treadmill, elliptical, bike and rower are first-class, not an afterthought. Outdoor runs, walks, rides and hikes record a route map coloured by the zone you were in — so you can see the hill where you tipped into threshold and the stretch where you finally settled.

ZONES THAT FIT YOU Zones are calculated from your age using the Tanaka formula, or from a maximum heart rate you've measured yourself. Use percentage of maximum, or the Karvonen scale if you know your resting heart rate. The app always shows which is in effect, because the two are not interchangeable.

KNOW IF YOU'RE DOING TOO MUCH Training load weighs your time by intensity — twenty minutes at threshold costs far more than twenty easy ones — and compares this week against your recent average. It answers the question a total-time figure never can.

ACHIEVEMENTS WORTH EARNING Twenty-two of them, some signposted and some left as surprises. Cumulative distance measured in landmarks. A weekly goal you set yourself, and reminders that assume life happened rather than telling you off.

COMPETE, PRIVATELY A weekly leaderboard among Game Center friends, ranked on minutes spent in a training zone. Only that one number is ever shared.

YOUR DATA STAYS YOURS No account. No server. No analytics. No third-party code of any kind. Your heart rate, workouts and routes live on your devices and in Apple Health, and nowhere else.

In The Zone is a training aid, not a medical device. Heart rate zones are estimates. If something feels wrong while exercising, stop and speak to a doctor.