Polar H10: the gold-standard interval strap.
For heart-rate interval training, the Polar H10 is as good as it gets: an ECG-accurate chest strap that responds fast and rarely drops out. It pairs with Stellar Intervals on iOS and Android and feeds the Norwegian 4×4 a clean 1 Hz signal.
Why it's the best for intervals
The 4×4 lives and dies on detecting when you cross 85% of max heart rate. A chest strap like the H10 reads the heart's electrical signal directly, so it's both accurate and fast — threshold crossings register within a beat or two instead of lagging like optical sensors can during hard, sweaty efforts. That precision is what makes each interval a true, repeatable dose.
How to pair it
- Moisten the electrode strips on the underside of the strap.
- Fit it snugly around your chest, just below the pecs, logo centered and upright.
- Open Stellar Intervals and pair the H10 over Bluetooth.
- Start a 4×4 — the app reads your live heart rate at 1 Hz and only counts the four minutes while you're above 85% of max.
H10 vs. other options
The H10 is the accuracy benchmark, but it's not the only way in. If you'd rather skip the strap, AirPods Pro 3 read heart rate from the ear on iOS, and Garmin sensors and watches broadcast over Bluetooth too. All work with Stellar Intervals — the H10 just sets the bar for hard, precise interval work.
Frequently asked questions
- Is the Polar H10 good for interval training?
It's the best consumer option. The H10 is a chest strap that reads the heart's electrical signal directly, so it's accurate and fast to respond — exactly what you want when an interval's effort depends on crossing a heart-rate threshold cleanly.
- How do I connect a Polar H10 to Stellar Intervals?
Wet the strap's electrodes, put it on snugly just below the chest, open Stellar Intervals, and pair over Bluetooth. Once connected, the app reads your heart rate live at one sample per second and runs the Norwegian 4×4 against it.
- Why is a chest strap more accurate than a wrist sensor?
A chest strap measures the heart's electrical activity (like an ECG), while wrist and optical sensors infer heart rate from blood-flow changes through the skin. The electrical signal is more accurate and reacts faster — especially during hard, sweaty intervals where optical readings can lag or drop out.
- Does the Polar H10 work on iPhone and Android?
Yes. The H10 broadcasts standard Bluetooth heart rate, so it pairs with Stellar Intervals on both iOS and Android.
Train at VO₂max.
Pair your Polar H10 and run a precise, repeatable 4×4 — the timer counts only while you're above 85% of max.