Apple Watch ships with a capable native Workout app. But the built-in experience has real limits when you want heart rate zone breakdowns, competitive elements, or meaningful training insights. Here's what to look for — and the best apps doing it well.
What to look for in an Apple Watch workout app
Before downloading anything, decide what you actually need:
- Zone tracking — does the app show time spent in each heart rate zone (Z1–Z5)?
- Automatic sync — does it read from Apple Health, or do you need to start a workout inside the app?
- Insight depth — weekly trends, zone progression over time, effort history?
- Motivation layer — streaks, goals, social features, competition?
- Privacy — does the app share your health data with third parties?
Most apps check one or two of these boxes. Very few handle all of them.
The native Apple Fitness app
The best starting point — it's free, well-integrated, and shows a heart rate chart after every workout. But zone breakdowns are basic (it uses Apple's fixed zones, which can't be customised), there's no weekly aggregate, and the social features are limited to Activity sharing with friends. Good for casual tracking, not enough for deliberate zone training.
Strava
The undisputed king of running and cycling social — massive community, segment leaderboards, kudos culture. Heart rate data is displayed per workout, and Strava Premium adds a heart rate zone breakdown. The zones are customisable based on your max HR or lactate threshold test.
Best for: runners and cyclists who want community and route-based competition. Not great for strength training or mixed workouts.
Garmin Connect (if you have a dual setup)
If you use a Garmin device alongside iPhone, Garmin Connect pushes detailed zone data to Apple Health. The training load, Body Battery, and VO2 max estimates from Garmin are among the best in the consumer market. But this requires owning a Garmin device — it's not an Apple Watch app per se.
Training Today / HRV4Training
HRV4Training uses your iPhone camera to measure heart rate variability each morning and gives readiness guidance — when to train hard and when to recover. Useful for athletes who want data-driven periodisation. Works alongside any workout app rather than replacing one.
Underdog
Underdog is built specifically around heart rate zone tracking and competition. It reads all workout data automatically from Apple Health — running, cycling, strength, HIIT, swimming — breaks it down by Z1–Z5, and converts zone time into a weekly points score. That score goes into a league against other users.
What makes it different: the competitive layer. Instead of tracking your zones in isolation, your zone effort is compared to other people in a weekly league. Bronze to Diamond divisions, weekly promotion and relegation. It turns consistent zone training into something you compete at — which, for most people, is the most effective motivational structure.
Best for: anyone who wants an Apple Watch app that makes heart rate zone training competitive and social. Free to download, works with any workout type.
Which should you use?
For pure running and cycling with social motivation: Strava. For heart rate zone tracking across all workout types with competition: Underdog. They're not mutually exclusive — many people run Strava for route data and Underdog for zone competition simultaneously, since both read from Apple Health.
The most important thing is picking one accountability system and using it consistently. The app you'll actually open after every workout beats the "best" app you don't.