Heart Rate Zones: Underdog
Zone 2 Training & Leagues
Only for iPhone
Free · In‑App Purchases
iPhone
Underdog turns your Apple Watch heart rate data into a game. Every minute you spend in Zone 2 — the sweet spot for endurance and fat burning — earns you points. Compete in weekly leagues with friends and climb from Bronze to Diamond.
No manual logging. No ads. Just open the app once and your workouts sync automatically from Apple Health.
WHY ZONE 2?
Zone 2 training (60–70% of your max heart rate) is the foundation of every elite endurance program. It builds your aerobic base, improves VO2 max, and burns fat — without burning you out. The catch: most people train too hard to actually be in Zone 2. Underdog shows you exactly when you're in the zone.
FEATURES
* Automatic Apple Watch sync — workouts appear in seconds
* 5 heart rate zones (Z1–Z5) calibrated to your max HR
* Weekly leagues: Bronze, Silver, Gold, Platinum, Diamond
* Points for every Zone 2+ minute
* Achievements, streaks, and personal records
* Friend leagues — invite via link
* VO2 max tracking from Apple Health
* Works with running, cycling, rowing, hiking, and 40+ workout types
FREE
Underdog is free to use. Optional Underdog Pro unlocks unlimited friend leagues, advanced stats, and custom zones.
TERMS & PRIVACY
Terms of Use (EULA): https://tryunderdog.com/terms
Privacy Policy: https://tryunderdog.com/privacy
Subscriptions auto-renew unless cancelled 24 hours before the end of the current period. Manage in Settings → Apple ID → Subscriptions.
Ratings & Reviews
- This app hasn’t received enough ratings or reviews to display an overview.
- Various fixes and improvements
The developer, Ignas Velza, 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 Used to Track You
The following data may be used to track you across apps and websites owned by other companies:
- Usage Data
Data Not Linked to You
The following data may be collected but it is not linked to your identity:
- Usage Data
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
- Seller
- Ignas Velza
- Size
- 25.2 MB
- Category
- Health & Fitness
- Compatibility
Requires iOS 26.0 or later.
- iPhone
Requires iOS 26.0 or later.
- iPhone
- Languages
- English
- Age Rating
4+
- 4+
- Infrequent
Contests
- In-App Purchases
Yes
- Premium (Lifetime) $99.99
- Premium (Weekly) $2.99
- Premium (Annual) $29.99
- Copyright
- © 2026 Ignas Velza