Most vocal warm ups at some point include a maximal stretching and opening of the mouth into something like a wide-open "Ah . . . ," generally accompanied by an expansive gesture such as thrusting out the chest and throwing back the head a bit. As long as you work your way up to it gradually, most learners will come along with you and at least give it a try. In warming up the class for pronunciation or general spontaneous speaking work, getting to "Ah . . . " is a not a bad benchmark. I was delighted, thanks to the media coverage of the Olympics, to see that it is now universally interpreted as signifying 'victory!' I am proud to say that of the several warm ups I use, all generally conclude with a "Michael Phelps-like" low or back central vowel and pedagogical movement pattern not all that different from that pictured to the left. (If you haven't seen the 2009 ETS video I did, it is here. Caveat emptor, of course!) Yes!!!