Watch metric
Endurance Score
Endurance Score Definition
A number rating your ability to sustain effort over long durations, built from your training history. A premium Garmin feature.
The idea here is that after or during a run, your watch can give you an estimate of how much you've got left in the tank.
The idea being that it can guide decisions about pace or effort during longer runs.
In reality, it tends to show that as you run harder and longer, you get more tired. Which isn't a big surprise to most people.
When it helps
For marathon and ultra runners tracking long-range fitness or if you forget that running longer makes you more tired.
When it doesn't
Early in your running, where it has little to say and even less to act on.