What this result means
Grade-adjusted pace (GAP) estimates what a split would have cost on the flat. Uphill running costs more energy, so the flat-equivalent pace is faster than the watch pace. Downhill costs less, so the equivalent is slower.
This is an energy-cost estimate from a published polynomial, not Strava’s product and not a prediction of race time on a hilly course. Use it to interpret a hill repeat or a rolling long run.
The same 5:00/km effort is a faster flat-equivalent pace uphill and a slower one downhill. A steep climb at 6:30/km can be a harder aerobic load than 5:00/km on the flat. A screaming downhill 4:20/km can be easier than it looks.
Treadmill incline is a clean input. Outdoor GPS grade is noisy. Garbage grade in, garbage GAP out.
Calculation method
Minetti 2002 cost of running versus grade. Flat-equivalent pace = actual pace × (flat cost ÷ grade cost). Cite: Minetti, A. E., et al. (2002), Journal of Applied Physiology, 93(3), 1039–1046.
Results are estimates. The polynomial is for running, not hiking, and it is not a muscle-damage model for long downhills.
GAP does not know surface, wind, or how much you shortened your stride. It is not a race predictor for a hilly marathon. Pair it with ordinary pace if you need even-split targets on a certified flat course.
Frequently asked questions
What is grade-adjusted pace?
An estimate of flat-equivalent pace given your pace and the incline or decline, using Minetti’s energy-cost polynomial.
Why is uphill GAP faster than watch pace?
Climbing costs more energy per metre. The equivalent flat pace is quicker to reflect that cost. You did not actually run that faster on the hill.
Can I use GAP to predict a hilly race?
No. This is an energy-cost estimate for a given grade, not a course profile model or a finish-time predictor.