I have hundreds of activities from two Forerunner 35s. How do I delete them in bulk?
Try this: Can I delete just the activities from a single Garmin device from my Garmin Connect account?
Thanks for the suggestion. Unfortunately didn't work for me.
You could try asking the author of the script for assistance. Other than that you'll have to delete the activities in GC web one at a time (unless you are capable of writing your own script).