To import an activity, click the button next to “Add Workout” in the menu on the left.
Import .gpx and .tcx Files
Select the file you want to import, and the corresponding activity will appear in the list below.
As soon as you have selected a sport type, the activity will be uploaded automatically. If the import has been successful, there will be a green tick in the “Status” column and you will be able to view the activity in your account.
Note: The file must not be bigger than 7 MB.
You now have the option to import activities tracked with Garmin watches directly into your Runtastic.com account.
Please see here to find further information.