Garmin heart rate, in the 4×4.
Already in the Garmin ecosystem? Your HRM strap — or your Fēnix or Forerunner watch in broadcast mode — feeds Stellar Intervals a live heart-rate signal to run the Norwegian 4×4. Here's what works and how to connect it.
What works
- HRM-Pro / HRM-Pro Plus.Garmin's premium chest straps — accurate, broadcast standard Bluetooth heart rate.
- HRM-Dual. The simpler dual-band chest strap; broadcasts Bluetooth heart rate out of the box.
- Fēnix / Forerunner watches.Turn on heart-rate broadcast mode and the watch's wrist sensor transmits over Bluetooth.
Turning on broadcast mode
On a Fēnix or Forerunner, open the controls menu (or Sensors & Accessories) and select Broadcast Heart Rate. The watch starts transmitting its heart-rate reading over Bluetooth; open Stellar Intervals and pair to it like any monitor. (Menu wording varies slightly by model and firmware.)
Strap vs. wrist
For the 4×4, a chest strap is the better choice — the optical wrist sensor can lag or drift during hard, sweaty efforts, exactly when detecting the 85% threshold matters most. Broadcast from the watch when it's what you have; reach for the HRM-Pro or a Polar H10 when you want the cleanest interval data.
Frequently asked questions
- Which Garmin heart-rate devices work with Stellar Intervals?
Any Garmin device that broadcasts standard Bluetooth heart rate: the HRM-Pro and HRM-Pro Plus, the HRM-Dual chest strap, and Fēnix and Forerunner watches when you turn on heart-rate broadcast mode.
- How do I broadcast heart rate from my Garmin watch?
On most Fēnix and Forerunner watches, open the controls menu or Sensors & Accessories and choose 'Broadcast Heart Rate' (sometimes under a Broadcast During Activity setting). The watch then transmits your heart rate over Bluetooth, and Stellar Intervals can pair to it like any other monitor.
- Should I use a Garmin strap or my watch's wrist sensor?
For hard intervals, a chest strap (HRM-Pro or HRM-Dual) is more accurate and responsive than the watch's wrist optical sensor. The wrist sensor via broadcast mode is convenient and fine for steadier efforts, but the strap is better when crossing the 85% threshold cleanly matters.
- Does this work on iPhone and Android?
Yes — as long as the Garmin device is broadcasting standard Bluetooth heart rate, Stellar Intervals pairs with it on both iOS and Android.
Train at VO₂max.
Broadcast from your Garmin and run a real 4×4 — Stellar Intervals counts the four minutes only while you're above 85% of max.