Zone 2 training with a strap and an iPhone

By Andreas B. Diendorfer · ORCID · LinkedIn · Updated 27 October 2026

Short answer

Pick a zone 2 range, set a ceiling alert at its top, and let the screen colour tell you when you drift above it. In Beatcast zone 2 is the Endurance zone, 60 to 70 percent of your maximum heart rate by default. The definitions differ between sources, so choose one on purpose.

Last checked: 12 October 2026.

Pick a range first

There is no single zone 2. Four common definitions give different numbers:

60 to 70 percent of maximum heart rate. This is Beatcast's Endurance zone.
60 to 70 percent of heart rate reserve, the Karvonen method.
Maffetone's 180 minus your age, which gives one ceiling.
A laboratory definition based on the first threshold, which can sit well away from any age formula.

The zone 2 calculator puts them side by side. If you have a measured maximum or a threshold from a test, use it. An age formula is an estimate, and it can be off by ten beats or more for one person.

Hold it with Beatcast

Connect a strap or arm band. See how to connect one.
Pick your zone profile. Training is worked out from your age. You can set a measured maximum, a resting rate or a threshold, and rename the zones.
Choose a target zone. Pick Endurance. While a session records, the line under the heart rate says In target, Above or Below.
Set a ceiling alert. It speaks up by sound, spoken value, haptic taps or a notification. A zone alert on Endurance adds a cue when you get there after the warm-up.
Start the session and put the phone away. The screen takes the colour of your zone, and the edges light up and pulse once when you leave your target.

An hour in zone 2 is an hour of not wanting to look at your phone. The Lock Screen and Dynamic Island keep the number where a glance finds it. See the Lock Screen guide.

History adds up your zone 2 minutes week by week. Weekly zone 2 minutes on iPhone shows where to find them.

What drift looks like

Over a long easy effort your heart rate tends to creep up at the same pace. That is common. When it creeps over your ceiling, slow down a little and watch the number settle. Do not chase it.

The talk test

Many people use a simple check alongside the number: can you speak in full sentences? It is a rough cue, and it works with a number or without one. Nothing in Beatcast measures it.

Why a strap

A strap or arm band sends about one reading a second, and the phone propped up in front of you shows it without a touch. Read the makers' own accuracy notes if precision matters to you.

Where Beatcast fits

Beatcast on the App Store. Fourteen days free, then one purchase. No subscription.

Questions

What is zone 2 for a 40-year-old?

By Beatcast's default, with the Tanaka estimate of maximum, 108 to 125 beats per minute. See the calculator for the others.

Can I do zone 2 without an Apple Watch?

Yes. See the guide to heart rate monitors without an Apple Watch.

Does the ceiling alert work with music playing?

Sound and speech lower the volume of your music for a moment.

Good to know

Beatcast is not a medical device. It is built for training and general wellbeing, and it cannot detect, diagnose, treat or monitor any condition. Its alerts are training aids, not a safety alarm. If you take medication that changes your heart rate or have a heart condition, ask your clinician before using age-based numbers.

The Bluetooth word mark is a registered trademark of Bluetooth SIG, Inc. Apple, iPhone, Dynamic Island and Lock Screen are trademarks of Apple Inc. All other names belong to their owners and are used only to say which sensors Beatcast can read. Beatcast is an independent product and is not affiliated with, endorsed by or certified by any of them.

Got it working? Report it in r/beatcast.