N4x4
Gold Standard for VO2 Max
Only for iPhone
Free · Designed for iPhone
iPhone
N4x4 - Norwegian 4x4 HIIT Trainer
Ready to transform your fitness? N4x4 brings you the scientifically-backed Norwegian 4x4 HIIT protocol—the most efficient way to boost your VO2 Max and build a bulletproof cardiovascular system.
WHY N4x4?
• It's set and forget: Press start, then just train. No fiddling with timers.
• Visual and audio cues guide you through every interval
• Perfect for beginners and advanced athletes alike
WHAT YOU GET:
• 5-minute warm-up to prepare your body
• 4 rounds of 4-minute high-intensity intervals
• 3-minute recovery periods between rounds
• Real-time heart rate zone display based on your age
WHY VO2 MAX MATTERS:
Your VO2 Max is the single greatest predictor of lifespan. Studies confirm high-intensity interval training like Norwegian 4x4 is the most efficient way to improve it. Top longevity experts (like Dr. Peter Attia) swear by it.
NO STRINGS ATTACHED:
• 100% free
• No sign-ups
• No ads
• No in-app purchases
• Just you and your workout
Download N4x4 now and start building a stronger, healthier heart today. Your future self will thank you.
Add the ability to manually adjust max heart rate and increased reliability of VO2 Max import from Apple Health.
The developer, Jan van Rensburg, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Collected
The developer does not collect any data from this app.
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
- Seller
- Jan van Rensburg
- Size
- 8.7 MB
- Category
- Health & Fitness
- Compatibility
Requires iOS 26.0 or later.
- iPhone
Requires iOS 26.0 or later. - Mac
Requires macOS 26.0 or later and a Mac with Apple M1 chip or later. - Apple Vision
Requires visionOS 26.0 or later.
- Languages
- English
- Age Rating
9+
- 9+
- Contains
Health or Wellness Topics
- Copyright
- © Jan van Rensburg