Peak Intervals

Guided 4x4 on Apple Watch

Free · In-App Purchases · Designed for iPhone. Not verified for macOS.

Train VO₂max with Norwegian 4x4 intervals. Guided workouts, Apple Watch support, and clear analytics for time-in-zone, recovery, repeatability, and training progress. Peak Intervals helps you train VO₂max using the Norwegian 4x4 interval method and track training quality over time. Run, ride, or row a 4x4 session, stay in your target heart rate zone, then review clear metrics that explain workout quality and progress over time. What you get: • Guided 4x4 workouts with Apple Watch support • Target heart rate zone guidance based on 90–95% of estimated HRmax • Time in Zone (≥90% HR) to measure intensity • Repeatability to see if you hold performance from interval 1 to 4 • Recovery to measure how fast your heart rate drops between intervals • Trends and simple verdicts like Improving, Stable, Under-target, or Fatigued • Workout history with interval breakdowns and session details Apple Health Peak Intervals can read workout and heart rate data from Apple Health (HealthKit) to compute your metrics and trends. You control what is shared at any time in iOS Settings. Subscriptions Peak Intervals offers an auto-renewing subscription with monthly and yearly plans, including a 2-week free trial where available. After the trial, an active subscription is required to start new workouts. Payment is charged to your Apple ID account at confirmation of purchase. Subscriptions renew automatically unless canceled at least 24 hours before the end of the current period. You can manage or cancel your subscription in App Store account settings. Peak Intervals is not a medical device and does not provide medical advice. High-intensity exercise may not be appropriate for everyone. Consult a physician before beginning a new training program. Privacy Policy: https://peakintervals.app/privacy Terms of Use: https://peakintervals.app/terms

Ratings & Reviews

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We’ve improved onboarding to make Peak Intervals easier to get started with, including clearer guidance for Apple Watch setup, a better explanation of workout analytics and progress tracking, and a smoother path for athletes using iPhone only. This update also improves sign-in and account creation with better email/password handling and smarter password autofill support. On Apple Watch, live workout guidance is now more reliable, with clearer heart rate target feedback and improved syncing of workout state and metrics.

Version 1.2.3

The developer, Justin Polidori, 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 Linked to You

    The following data may be collected and linked to your identity:

    • Health & Fitness
    • Contact Info

Privacy practices may vary based, for example, on the features you use or your age. Learn More

Accessibility

The developer has not yet indicated which accessibility features this app supports. Learn More

Information

Seller
  • Justin Polidori
Size
  • 12.4 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.
  • Apple Watch
    Requires watchOS 26.0 or later.
Languages
English and 5 more
  • English, French, German, Italian, Portuguese, Spanish
Age Rating
16+
In-App Purchases
Yes
Copyright
  • © 2026 Justin Polidori
  • Privacy Policy

    • More by Justin Polidori

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