Although this post is old, it did lead me to tapiriik.com which looks interesting. Unfortunately, tapiriik.com shows this message:
"Due to new limitations in Garmin Connect's API, tapiriik can no longer upload activities to your Garmin Connect account, download historical activities from before you connected to tapiriik, or detect private acitivites (all activities uploaded to your Garmin Connect account will be synchronized)."
Given that I'm looking to synchronize my historical activities from Garmin Connect to Strave, it looks like it does not meet my needs.
