I studied Tai Chi for several years with a local instructor, who had learned the styles she taught from the descendants of the founding families in mainland China. She's a slight thing, maybe 5'6" and 120 pounds, but practicing Wu style "push hands" with her was like fighting liquid steel - like that dude from the 2nd Terminator movie - she could've thrown me through the wall at any given instant. Balance, timing, and applying force only when and where necessary are key. She knew my center of balance and next movements better than I did.