Name: Run Efficiency with GAP
Rating: 5 (3 reviews)
Author: litdev

This data field combines Grade Adjusted Pace (GAP) and Running Efficiency (RE). See https://support.garmin.com/en-US/?faq=gyywAozBuAAGlvfzvR9VZ8 for generic instructions installing data fields, this one should work with running and walking activities only.

GAP is calculated using either the method by Minetti (equal energy) or that used by Strava (equal heartrate), see https://medium.com/strava-engineering/an-improved-gap-model-8b07ae8886c3 .  Additionally, I added an uphill and downhill GAP multiplier setting. The gradient is calculated from elevation data over the previous 30 seconds (can be modified by settings) using a least squares fit. The accuracy is clearly dependent on the avaraging duration period and watch capabilities using GPS and barometer to estimate elevation.

RE is defined by speed/heartrate, and therefore it makes sense to use GAP modified speed to account for gradient.

There are other nice IQ data fields that calculate GAP or EF but not combined, I think. The combined GAP/EF is an interesting parameter for running and walking, comparing different routes, effort levels, condition or recovery.

Additionally, the FIT file reports the calculated gradient (%), GAP multiplier, RE (m/hb) and GAP (min/km) for visualisation in Garmin Connect or further analysis. Note that IQ FIT reporting data is decimal, so for example GAP 4.75 is 4:45 in min:sec/km.

Set options with Garmin Connect IQ app or Garmin Express.

Any questions or suggestions, please Contact Developer or leave a review.