Normalized Graded Pace

Definition

“Normalized Graded Pace” (NGP) is the running pace that would have caused the same physiological load on flat ground as the pace actually run, including all climbs, descents, and changes of speed. It is the running counterpart of Normalized Power in cycling.

NGP corrects for two things: terrain (running uphill at the same pace is much harder) and variability (intervals load the body more than a steady run with the same average). The term comes from TrainingPeaks.

Why it matters

Raw pace is a poor measure of load as soon as the course is not flat. A trail run at 6:30 min/km with 800 m of climbing can be harder than a flat run at 4:45 min/km. Rating both by average pace massively underestimates the trail run.

NGP makes runs on different courses comparable and provides the basis for computing Intensity Factor and Training Stress Score for running. Without it, load curves such as CTL and ATL would be systematically skewed for runners in hilly terrain.

How obseed measures it

obseed computes NGP in two steps from one-second GPS and barometric altitude data:

1. Grade correction: convert each second's pace into an
   equivalent flat pace based on the gradient
2. Normalisation: as for Normalized Power, using rolling
   30-second averages and the fourth power

For the grade correction obseed uses a cost-of-running model in which energy cost per kilometre rises with gradient and falls slightly on moderate descents. On steep descents the cost rises again because eccentric muscle work dominates.

These values are approximations and vary between individuals. obseed places NGP in zones using the threshold pace from treadmill spiroergometry, not an estimated threshold pace from a field test.

Example

A runner covers 10 km in 55:00, an average pace of 5:30 min/km. The course has 5 km at +6 % and 5 km at −6 %.

After grade correction, the mean equivalent flat pace is about 4:51 min/km. Normalising the changes of speed weights the fast downhill section further, so NGP lands around 4:48 min/km, 42 seconds per kilometre faster than the raw pace.

With a threshold pace of 4:40 min/km from the treadmill test, this was a run just below threshold, not the easy base run the raw 5:30 min/km suggests.