To elaborate, and I'm not sure anyone would want to do this too often. Strava works very well for syncing from Garmin to Strava, but the other way around, Strava to Garmin is typically not worth the effort. However, if you're up to it.
I've done this on my iPad and was able to get it to Garmin connect. . .
Install the Strava iPhone app on your Apple mobile device
Complete an activity using the Strava app
Login to Strava site
Open the activity then click "GPX" on the map to download the gpx file. You'll need to have a paid Strava (summit) account to do this.
Open Garmin Connect web site
Click the "Upload or Import activity" icon then select "Import Data"
Drag the downloaded GPX file onto the "Drop files here" section
Click import data
If you get errors, you'll need to run it through another utility like plotaroute.com to get it to play nicely with Garmin (this is how I did it, since I did initially get errors on the gpx file downloaded from Strava)
