Ramp4x4: VO2 Max Trainer

Train VO2 max the proven way. Ramp4x4 runs the Norwegian 4x4 for you: one tap loads the full session and your Apple Watch cues every interval, so you just train.

Ramp4x4 is the easiest way to run the Norwegian 4x4, the interval workout most studied for raising VO2 max. One tap loads the whole session and coaches every phase on your Apple Watch, so you train heads-up instead of doing zone math with a stopwatch.

It does one thing and does it well. This is not a general fitness app. It is a purpose-built trainer for the Norwegian 4x4: a warmup, four 4-minute hard intervals at 85% to 95% of your max heart rate, three-minute recoveries, and a cooldown.

THE WORKOUT • One-tap Norwegian 4x4, set up for you • Big countdown and current phase, always on screen • Per-phase coaching so you know when to push, hold, and recover

APPLE WATCH FIRST • Haptics and voice cues at every phase change, so you feel the switch instead of watching the clock • Live heart rate against your target zone • Your iPhone mirrors the workout and can take over if the watch drops

HEART RATE, DONE FOR YOU • Target zones from your max heart rate, measured or estimated • Optional heart-rate-reserve (Karvonen) targeting • Works with Apple Watch or an external Bluetooth chest strap

AFTER THE WORKOUT • Summary and shareable card: total time, average HR, peak HR, and time above 90% of max HR • A 0 to 100 quality score for the session • A per-workout VO2 max estimate and your trend over time • Saves to Apple Health

FREE AND PREMIUM Free includes the full Norwegian 4x4 on Apple Watch, live heart-rate coaching, voice and haptics, Apple Health sync, and the post-workout summary. Premium (monthly or yearly) adds full workout history, VO2 max trends, the detailed quality-score breakdown, custom presets, a guided multi-week plan, and smart ramp modes.

WHY NOT JUST USE A TIMER You can run a 4x4 with a stopwatch or Apple Fitness, but you have to build the nine phases yourself and watch both the clock and your heart rate while gasping. Ramp4x4 already knows the protocol and your zones, and cues every transition for you.

PRIVACY Your heart-rate, workout, and location data stay on your device and in Apple Health. We never sell your data.

Ramp4x4 Premium is an auto-renewable subscription. Payment is charged to your Apple ID at confirmation of purchase and renews automatically unless canceled at least 24 hours before the end of the period. Manage or cancel in your App Store account settings.

Ramp4x4 is a training tool, not medical advice. The 4x4 is intense, so build up gradually and talk to a doctor before near-maximal intervals if you have any heart concern.

Terms of Use (EULA): https://www.apple.com/legal/internet-services/itunes/dev/stdeula/ Privacy Policy: https://bc1224.github.io/Ramp4x4/privacy-policy.html