Norwegian 4x4 Coach guides you through the science-backed Norwegian 4x4
interval workout using your live heart rate: a warm-up, four 4-minute hard
intervals with recoveries between them, and a cool-down, with short spoken cues
that keep you in the right range.
Requirements
An iPhone running a compatible version of iOS
A Bluetooth heart-rate sensor (for example a Polar H10, Verity Sense, or
OH1, or any standard Bluetooth heart-rate strap)
Getting started
Put on your heart-rate sensor.
Open the app and tap Start. It connects to the first
sensor it finds.
Follow the spoken cues through each phase.
To tune the workout (max heart rate, per-phase target ranges, phase durations,
number of intervals, the coaching voice, and the wording of the spoken cues) or
to pin a specific sensor, open Settings (the gear icon).
Sharing your data
After a workout, tap Share session data to export that
session's raw data: your heart rate over time, the phase and target zone at each
point, and your settings. It uses the standard share sheet, so you can send it to
Mail, Messages, Files, or an AI assistant to review your effort and time in zone.
The app does no analysis itself, and the data leaves your device only when you
choose to share it.
Troubleshooting
Sensor won't connect: make sure the strap is on and awake
(a little moisture on a chest strap's electrodes helps), Bluetooth is on,
and the sensor isn't already connected to another app.
Wrong sensor connects: if several sensors are nearby, pin
yours in Settings → Sensor.
No heart rate shown: confirm the sensor is reading (most
have an LED or companion app) and reconnect from the app.
Safety: Norwegian 4x4 Coach is a fitness tool, not a medical
device, and does not provide medical advice. High-intensity exercise carries
risk. Consult a physician before starting any new exercise program, and stop
if you feel unwell.