Although it is not supported for direct upload to Strava, it is possible to upload from your Garmin GPS 60Csx device.
- Clear track log, turn tracking ON
- When activity is complete, turn tracking OFF
- NOTE: do NOT clear the track log even if you have saved the track. You can turn tracking off to separate multiple activities.
- Connect the unit to PC, and using Garmin BaseCamp or another program, export the "ACTIVE LOG 001" as .gpx.
- If there are multiple active logs, you will see "ACTIVE LOG 001", "ACTIVE LOG 002" etc., typically one for each time you turned tracking ON and OFF. Click on each to confirm the track on the map (sometimes ACTIVE LOG tracks are created that are single points or otherwise not meaningful data); each can be exported as separate GPX file including the timestamps required for import to STRAVA.