Underdog

Underdog is a heart-rate zone training app built for Apple Watch, turning every minute in Z1–Z5 into points automatically. Connect Apple Health once, wear your watch, and your heart-rate data syncs after workouts—so you never have to log manually.

You earn points for time spent in each zone, with Zone 2 building your aerobic base and higher zones scoring more. Running, cycling, strength, and HIIT all count, and you can view a full Z1–Z5 breakdown to understand where your effort went.

Compete in weekly Bronze→Diamond leagues where points reset each week. Create private leagues with an invite code to race friends, and track weekly insights like zone breakdowns, step trends, and an intensity timeline.

Do I need to manually log workouts or heart-rate data?

No. Underdog reads heart-rate and workout data from Apple Health, syncing automatically after workouts so there’s no manual logging.

Which devices and sensors does Underdog support for heart-rate syncing?

Underdog works with Apple Watch via Apple Health. Heart rate and workout data can also sync from other connected sensors that feed into Apple Health.

How does the scoring work across heart-rate zones?

Every minute spent in zones Z1–Z5 earns points. Zone 2 builds your aerobic base, while Zone 3 and above score higher.

How do leagues and weekly promotions work?

You start in Bronze and climb to Diamond based on your zone points. Each week points reset—consistent performance lifts you, while slack performance can drop you.

Can I compete with friends in a private league?

Yes. Create a private league and share an invite code so friends can join and compete with real-time rankings.

Is the app free, and are there ads?

Underdog is free and runs with no ads.