Norwegian 4×4 Cycling

Norwegian 4×4 is an indoor cycling app for smart trainers. It runs the Norwegian 4×4 interval protocol — four 4-minute work blocks at 90–95% of maximum heart rate, with 3-minute active recovery in between — and controls your trainer's resistance automatically so your heart rate stays in the zone. This is not a running app. Watts, cadence, ERG control — built for the bike. HEART-RATE ERG CONTROL Most training apps set a fixed wattage and leave you to manage your heart rate. Norwegian 4×4 works the other way: it adjusts target watts every block to land your HR in the 90–95% HRmax band. • Adjustments happen in small steps — no jarring shifts mid-block • Cardiac drift across blocks is detected and compensated automatically • Cadence protection prevents the ERG death spiral if you lose power • Lock the target manually to ride fixed watts whenever you want TRACKS YOUR PROGRESS Power at target HR is the headline metric. Each session, the app asks: how many watts did it take to hold 90–95% HRmax? That number, plotted over weeks, shows whether you're getting fitter. The app builds a rolling 8-session trend once four sessions are logged. Sessions with poor HR-band adherence are excluded automatically. No streaks, no badges — just the number. HEALTHKIT INTEGRATION Sessions save to Apple Health as indoor cycling workouts with full HR sample data. VO₂max, resting heart rate, and body mass are read at session start to calibrate targets. No account required. No cloud. Your data stays on your device. HARDWARE COMPATIBILITY Works with any Bluetooth smart trainer. Confirmed working with Jetblack and Wahoo. Heart rate via your trainer's built-in HR bridge or any BLE heart rate sensor. ONE-TIME PURCHASE. NO SUBSCRIPTION.