GearMove in Zone 2
Heart rate monitors for Zone 2 training
Zone 2 lives in a narrow band of heart rate, so the sensor you trust matters more than the watch on your wrist.
In a study of 50 adults, a chest strap agreed almost perfectly with an ECG across treadmill, bike and elliptical sessions, while wrist-worn optical monitors were less consistent 1.
A chest strap reads the electrical signal of your heart, like an ECG does; an optical sensor uses light to follow blood flow under the skin 1. Either can guide an easy steady session. For intervals and numbers you can rely on, a strap is the safer buy.
What to look for
Electrodes for accuracy
The study authors recommend an electrode chest monitor whenever an accurate heart rate matters 1.
Optical works, with limits
Optical accuracy depended on the activity: it was best on the treadmill and lowest on the elliptical 1.
Two ways to connect
Look for both Bluetooth and ANT+, so one sensor talks to your watch, phone, bike computer and gym machines. The Polar H10, for example, supports both 3.
A battery you can swap
Coin-cell straps run for a long time between changes: the Polar H10 is rated at 400 hours on a CR 2025 cell 3.
Fit you forget about
A strap should sit snug just below the chest muscles. If a hard strap chafes, try a soft textile one or an arm band for easy days.
Worth a look
- Chest strap
Polar H10
Against an ECG Holter it detected 99.6% of heartbeats correctly, and 99.4% during high-intensity activity; the study was partly funded by Polar 2. It connects over Bluetooth and ANT+ 3.
Best for Accuracy, intervals and HRV
- Chest strap
Garmin HRM-Pro Plus
Garmin's own chest strap: the natural pairing if you already train with a Garmin watch. Check it supports the watch you own.
Best for Garmin watch owners
- Chest strap
Wahoo TICKR
A simple chest strap that many people use with indoor trainers and training apps. Check it pairs with your watch or app before you buy.
Best for Indoor cycling and apps
- Optical arm sensor
Polar Verity Sense
Worn on the upper arm instead of the chest. Optical sensors follow blood flow with light, so expect less precision in hard intervals than from a strap 1.
Best for Comfort on easy Zone 2 days
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Questions people ask
Is my watch's wrist sensor good enough for Zone 2?
Often, for steady sessions. Accuracy varies by device and activity: in one study, optical monitors trailed a chest strap and did worst on the elliptical 1. If your numbers jump around, a strap settles it.
Chest strap or arm band?
A chest strap reads the heart's electrical signal and agreed best with an ECG 1. An arm band is optical: comfortable, and fine for easy work.
Do I need a heart rate monitor at all?
No. The talk test works: the point where speech first becomes difficult lines up with the ventilatory threshold 4, and Zone 2 sits below it. A monitor helps you stay honest on easy days and measure hard intervals.
Sources
- Gillinov S, Etiwy M, Wang R, et al. Variable accuracy of wearable heart rate monitors during aerobic exercise. Med Sci Sports Exerc. 2017;49(8):1697–1703.
- Gilgen-Ammann R, Schweizer T, Wyss T. RR interval signal quality of a heart rate monitor and an ECG Holter at rest and during exercise. Eur J Appl Physiol. 2019;119(7):1525–1532.
- Polar Electro. Polar H10 user manual: technical specifications and care instructions. support.polar.com. Accessed 2026-11-04.
- Persinger R, Foster C, Gibson M, Fater DC, Porcari JP. Consistency of the talk test for exercise prescription. Med Sci Sports Exerc. 2004;36(9):1632–1636.
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