Holy molly. I thought Garmin would provide a fancy and "updatede" procedure for uploading and/or extracting data from the fancy Garmin 910XT... but no. You need to search for a while before you find the gold. First I thought you could find a garmin connect tool or plugin for Firefox, but that failed completely. Then I narrowed down my search to "forerunner 910xt linux" (without the quotation marks in google). I found some sites that suggested to download a lot of python stuff and get things directly from Git.