^ What should actually be done in these cases is use an Acrobatics (Str) check. Or I suppose an Athletics (Dex) check. Either one could reasonably describe parkour. As Niara said, muscles are certainly involved in jumping, so str or athletics should be involved somehow.
But yeah, if you have no walls to run along or rails to propel yourself off of then the argument for something other than an Athletics (Str) check gets more difficult. Maaaaaybe you could use an Athletics (Dex) check - you've trained in long jumping giving you proficiency in athletics, but your key to success is exact proper placement of your feet when running and for the final launch.
