What Is the Durability Score?
The Durability Score is one number: the percentage of your fresh 12-minute power you can still produce when fatigued.
Cadence and heart-rate changes are reported for context, but the score itself comes solely from power.
In other words, it tells you exactly how much of your wattage you keep when it really counts—late in a race, on a long training day, or during back-to-back rides.