Viking 4x4 vs the Apple Workout App

Honest answer first: an Apple Watch alone works fine for casual Norwegian 4x4 use. Build a Custom Workout with 4-minute work and 3-minute recovery blocks, glance at your wrist, and go. If that's all you need, you don't need another app.

A dedicated protocol app earns its place when you care about execution and proof. The Workout app doesn't coach you into the 85–95% zone, doesn't break the session into intervals afterward, and reports at most a single recovery number after you end a workout — not the per-interval heart rate recovery measurements that show adaptation, and no trend of them over weeks.

Viking 4x4 uses the same sensors — your Apple Watch streams live heart rate into the app — and adds the protocol brain on top: phase guidance in your ears, a gold target chip when you're in the zone, and the interval report that tells you whether the number that matters is moving.