VO₂ max is how much oxygen your body can use during hard exercise. More oxygen = more energy = you can run faster, longer, and with less effort. Another simple way to say it: It’s your engine size. Bigger engine → better performance, better endurance, and better long-term health. 🇳🇴 What Is the Norwegian 4×4? It’s a high-intensity interval training protocol developed by Norwegian exercise physiologists to rapidly improve VO₂ max and cardiovascular fitness. Many elite endurance athletes use it because it pushes the heart into the zone where it adapts the fastest 90–95% of max heart rate without completely destroying your body. How It Works You perform 4 intervals, each lasting 4 minutes, at a high but controlled intensity. Between each interval, you recover for 3 minutes at an easy pace. Structure 1. Warm-up: 5–10 minutes easy 2. 4 minutes hard (90–95% max HR — fast but sustainable) 3. 3 minutes easy (60–70% max HR) 4. Repeat that for 4 total rounds 5. Cool down: 3–5 minu...