Somehow I don't think it's very hard. I've met personal trainers that don't know shit. But then I've met personal trainers that were sharp. Take it for what it's worth. You should do a search on the net.
A goofball ex of mine took a course .. he's too stupid to pass the test, however I'm going to get my hands on all the materials they gave out at the course .. I'll be happy to share.