When I was in the service I went to a few.
Though it seemed they concentrated one only one muscle. (not the one's that were sore either)
A Girl that worked with me awhile back got her certificate and SHE gave nice one's!! (The REAL deal, and it felt GREAT)
I actually went to school myself for it, but never got my licence. (Long LONG story involving ex-girlfriend and her coke dealing new boyfriend (which she had just left and returned to me), and the people he got it from looking for their $$$.............