Because Garmin did not calculate one, and there is nothing in the file it could have shown instead. Training Effect, training load and the other training metrics are not stored in the ride file. Garmin calculates them after the ride arrives, from the ride’s details, and only for rides it accepts as coming from your own device or from a listed platform. An uploaded ride that Garmin does not accept that way shows distance, heart rate and power, and an empty space where Training Effect would be.
Is Training Effect stored in the FIT file?
No. On 12 September 2026 we read two ride files field by field: a Wahoo ride from 31 August 2026 and a Zwift ride from 9 September 2026. Garmin Connect showed a Training Effect for the Zwift ride and none for the Wahoo ride. Neither file had a Training Effect, training load or stress field in its session summary. On 27 September 2026 we read two more Zwift files fetched from Garmin Connect and two Wahoo files fetched from Wahoo, with the same result: none of the four carries such a field. What they do carry is one record per second with heart rate, power, speed, distance and altitude, plus laps, a session summary, events and the recording device.
Where is it calculated, then?
On your Garmin device. Garmin’s support page Can Third-Party Activities Impact My Garmin Training Metrics? describes the order: the device downloads the activity details on the first sync, calculates your new training metrics from them, and uploads the result to Garmin Connect on the second sync. According to the Forerunner 570 owner’s manual, Training Effect technology is provided by the Garmin Human Performance Lab, with heartbeat analytics by Firstbeat.
Why does that matter for a ride from another device?
Because there is nothing to copy. A sync tool cannot carry Training Effect from Wahoo to Garmin, since Wahoo’s file never had it. The only question is whether Garmin calculates it for your ride, and that depends on which device the file names, as described in why an uploaded ride does not count toward Training Status.
Would a file with a Training Effect field help?
Our measurement gives no reason to think so. Garmin showed a Training Effect for a Zwift file that has no such field, so it does not need one. Whatever a file might carry, the numbers on your watch are the ones Garmin calculates.
What does this mean when Nabe transfers a ride?
Nabe leaves the ride data untouched and changes only the device named in the file. Garmin then does what it does with your watch’s own rides: it calculates. The numbers on your watch are Garmin’s numbers, not Nabe’s.