MapMyFitness is the umbrella under which Under Armour has united the group of apps it purchased, which include MapMyRide, MapMyWalk, MapMyRun etc.

Your login credentials for any of these apps will allow you to connect through the MapMyFitness, despite the mis-match in branding. So you can connect your existing MapMyRun/Walk/Ride etc. account using the MapMyFitness option on the Connect Apps page of your Dashboard.