It may have been something that Ken put in the intro dialoge as a homage to the comic book. Maybe a bit of a pacifier for his consultant, Stan? In any event, like Paul, I really don't see the increase in strength you all are referring to in the series. I still think that the tv Hulk was just more restrained than the comic book Hulk. He had all that strength in plenty all the time, he just didn't use his full power most of the time. Only in times of real need do we see him "give it his all".