Recovery Timer is an app that helps you do workouts - weight lifting, running, HIIT, fartleks - that use sets. You perform your workout as usual, and the app uses your heart rate to figure out how long your rest period will be.
You can specify your:
- workout type
- typical resting time (what you would usually do, like “3 minutes”)
- recovered heart rate (what your heart rate should drop down to for the next set to begin)
- when to transition (this can be heart-rate alone, time alone, or both)
It’s not rest, it’s recovery.
You can learn more on the Apple App Store and download Recovery Timer for Apple Watch there.