Quote Originally Posted by TrumpetTheKid View Post
Did he really have a muscle disorder? I thought he just played in a weird way due to lack of a formal teacher (of course he still ended up being awesome despite that!).

To answer the original posters question, I think that an air pocket would limit flexibility since with the lip puffed out like that, you would lose the ability to contract and relax your lip muscles making it more difficult to shift notes smoothly.
When I initially started to play, I too filled my cheeks and was directed not to, but told if I continued I would stretch my cheeks with exertion a consequence like Dizzy's.

Yes, from time to time air is now pocketed between my teeth and inner lip area, but it is not constantly there nor is it exerted, its just a reserve and expended as I play. I don't feel that it messes up my note transition or anything else about the way I play. Too, it's less now with my new upper denture, thus I may have to reset the breath marks on my music.