Viking 4x4

4 minutes hard. 3 minutes easy. Repeat 4 times. Finish strong. Viking 4x4 is the interval coach built around one protocol — the Norwegian 4x4 — the workout researchers used to raise VO2 max faster than steady cardio and, in a two-year trial, reverse decades of cardiac aging. No bloated workout library. No guesswork. Just the protocol, coached by your heart rate, with proof at the end that it is working. HOW IT WORKS • Set your session — warm-up, four hard intervals, easy recoveries, cool-down. The 45-minute default is the exact protocol from the research. • Press Start — your Apple Watch app launches itself and streams live heart rate to your iPhone. No fiddling with the Watch mid-workout. • Follow the coach — voice cues and haptics tell you when to push, when to ease off, and when the next interval is coming. Never look at a screen while you train. • SKÅL — every session ends with your…