OrangeMat - 2007-08-04 6:31 AM
The opposite of expansion is contraction. Think inhale as opposed to exhale. Organic vs. muscular energy. That sort of thing.
In all of the reading I've done regarding the chakras, I haven't come across expansion as a concept that particularly corresponds the vissudha chakra. But then again, I'm still learning myself. The fifth chakra is the throat chakra, and relates to communication and creativity, as well as truth. So obviously poses that open the throat (ustrasana is the most obvious example) could serve you well in your class.
You might want to look here for some inspiration for your class. Also, this page might have some additional insight for your theme as well (do a find on the word "fifth"). Good luck!