I did another detailed comparison today with a road cycling activity from an Edge 1040:
Garmin Connect original FIT: ~719 kB
FIT received by Intervals via Garmin API: ~601 kB
The actual recording itself seems intact — same number of record samples, and the important raw data like power, HR, cadence, GPS, altitude, temperature, etc. is still there.
My Connect IQ / developer fields such as a second power meter stream (Power2) and gearing data were also still present.
But quite a few Garmin-specific fields/messages were missing from the API version, including:
- Stamina / Potential Stamina
- Performance Condition
- Aerobic / Anaerobic Training Effect
- Recovery Time
- Garmin VO2max
- Estimated Sweat Loss
- Primary Benefit
- some sensor/device metadata
- workout / workout_step messages
There were also several Garmin/proprietary message types missing completely which I couldn’t reliably identify.
So the core training data is still there, but quite a useful Garmin-specific analysis layer is lost.
For this test I deleted the auto-imported activity first and then uploaded the original FIT from Garmin Connect. The additional data was picked up correctly — for example the workout steps are present again.
@david — would it also work to simply upload the original Garmin FIT over the already existing auto-imported activity, without deleting it first?
Ideally Intervals would recognize it as the same activity and just replace/enrich the FIT data instead of creating a second activity.
If that works, it would be a very practical workaround for important rides: let the normal Garmin sync happen, and only upload the original FIT afterwards when the Garmin-specific fields are needed — without having to delete and re-import the activity first.