Norwegian 4x4 Interval Timer

Norwegian 4x4 is a dead-simple timer for the interval protocol with the strongest evidence behind it: four 4-minute hard efforts separated by 3-minute recoveries, after a 5-minute warm-up. Press Start and go — the app walks you through every phase with a clear countdown, gentle 10-second warnings, and 3-2-1 cues. WHY THE 4x4 Popularized by Norwegian sports scientists and now recommended widely for building VO2max — the single fitness number most tied to longevity. You work hard for four minutes, recover for three, repeat four times. About 40 minutes including warm-up, done 1–3 times a week. WHAT YOU GET • Full-screen countdown you can read from across the room • Chime, screen-flash, or silent alert modes — flash mode is made for treadmills and shared gyms • Haptic taps at the 10-second warning and the 3-2-1 countdown • A quick 4x30s mode for short days, plus adjustable sprint and rest lengths • Workout calendar: every session marks a circle on your month — watch your streak grow • Screen stays awake for the whole session WHAT YOU DON'T GET • No account. No subscription. No ads. No analytics. No permissions. • Your history lives on your phone and nowhere else. • Works completely offline, forever. Buy it once, sweat four times a week.