NTRVL: 4×4 Trainer
Norwegian 4×4 VO2Max Training
Free · In‑App Purchases · Designed for iPhone. Not verified for macOS.
Your AirPods Pro 3 are now a heart-rate trainer. The Norwegian 4×4 protocol — 40 minutes, twice a week, scientifically the fastest way to raise your VO₂ Max.
ADD YEARS TO YOUR LIFE IN 40 MINUTES A WEEK.
NTRVL is the cleanest way to do the Norwegian 4×4 — the interval protocol that 30+ years of research has shown to raise VO₂ Max faster than any other workout. And VO₂ Max isn't just a fitness number. It's the single strongest predictor of how long you live.
You don't need a gym. You don't need a trainer. You don't even need an Apple Watch. If you have AirPods Pro 3 or Powerbeats Pro 2, you already own a medical-grade heart-rate sensor — NTRVL just turns it into a coach.
THE PROTOCOL
• 10-minute warm-up
• 4 × 4 minutes in Zone 4 (90% max HR), with 3 minutes of active recovery between
• 5-minute cool-down
That's it. Forty minutes, twice a week. Backed by NTNU in Trondheim, where the protocol was developed.
WHAT NTRVL DOES
• Reads your live heart rate from AirPods, Powerbeats, or Apple Watch
• Calculates your personal training zones using Karvonen HRR + Tanaka max HR — auto-adjusted for your age, resting HR, and biological sex from Apple Health
• Adaptive warm-up — the next phase doesn't start until your heart is actually ready
• Real-time zone feedback so you know if you're working hard enough (and back off when you're not)
• Apple Watch companion — see your zone, BPM, and remaining time from your wrist
• Tracks every session in Apple Health as a real workout, with energy burned and HR samples
WHY VO₂ MAX MATTERS
Higher VO₂ Max is linked to lower risk of cardiovascular disease, dementia, type-2 diabetes, and all-cause mortality. A 5-point increase in VO₂ Max can add years of healthy life. The Norwegian 4×4 raises VO₂ Max more than any other protocol of equal duration. NTRVL gives you a structured way to do it for the rest of your life.
PRIVACY
Your heart-rate data never leaves your iPhone. No accounts, no servers, no analytics on your health. Everything is processed locally and stored in Apple Health, where you own it.
REQUIREMENTS
• iPhone running iOS 17 or later
• A heart-rate source: AirPods Pro 3, Powerbeats Pro 2, or Apple Watch (Series 4+)
• Optional Apple Watch companion app for wrist-based control
NTRVL Pro (free 7-day trial)
Unlock custom interval lengths, session history with PDF export, VO₂ Max trend charts, and training-load tracking.
ntrvl.app
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Terms of Use (EULA): https://www.apple.com/legal/internet-services/itunes/dev/stdeula/
Privacy Policy: https://www.ntrvl.app/privacy
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The developer, Andrii Gryshutkin, 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
- Andrii Gryshutkin
- Size
- 3.7 MB
- Category
- Health & Fitness
- Compatibility
Requires iOS 17.0 or later.
- iPhone
Requires iOS 17.0 or later. - Mac
Requires macOS 14.0 or later and a Mac with Apple M1 chip or later. - Apple Vision
Requires visionOS 1.0 or later. - Apple Watch
Requires watchOS 10.0 or later.
- iPhone
- Languages
- English
- Age Rating
4+
- 4+
- In-App Purchases
Yes
- NTRVL Pro Monthly $4.99
- NTRVL Pro Yearly $29.99
- Copyright
- © 2026 Andrii Hryshutkin minimotactu.com