Plain English: Use NTRVL to train smarter. Don't use it as medical advice. That's basically it.
By downloading or using NTRVL, you agree to these terms. If you don't agree, don't use the app.
NTRVL is a fitness app that guides you through the Norwegian 4×4 interval training protocol using real-time heart rate data from AirPods Pro 3 or Powerbeats Pro 2. It provides workout timing, HR zone tracking, and performance scoring.
NTRVL is not a medical device, and nothing in the app constitutes medical advice. The heart rate data, VO₂ Max estimates, and zone calculations are for fitness purposes only. Always consult a physician before starting any high-intensity exercise program, especially if you have a heart condition or other health concerns.
Heart rate readings come from Apple's HealthKit via AirPods Pro 3 or Powerbeats Pro 2. NTRVL does not control the accuracy of these readings. Optical heart rate sensors may produce inaccurate results during certain activities or for certain individuals. Do not rely on these readings for medical decisions.
High-intensity interval training involves physical exertion that carries inherent risks. By using NTRVL, you acknowledge that you exercise at your own risk. Stop immediately if you feel dizzy, faint, short of breath, or experience chest pain.
NTRVL offers a free tier and an optional Pro subscription. Subscriptions are managed through Apple's App Store and are subject to Apple's terms. You can cancel anytime through your Apple ID settings.
The NTRVL name, logo, design, and code are the property of NTRVL. The Norwegian 4×4 protocol itself is a published scientific method (Helgerud et al., 2007) and is not proprietary.
We may update, modify, or discontinue the app at any time. We'll do our best to keep it running and useful, but we make no guarantees of uptime or availability.
To the maximum extent permitted by law, NTRVL and its developers shall not be liable for any injuries, health complications, data loss, or damages arising from the use of the app.
We may update these terms from time to time. Continued use of the app after changes constitutes acceptance of the updated terms.
Questions? Email hello@ntrvl.app.