If you could do only one exercise activity for the rest of your life, what would it be? —Emilie Moore, NOBLESVILLE, IND. Mixed martial arts. It's a great way to stay fit, stay toned, stay lean. I love yoga, but the namaste thing only takes you so far. Every now and again, you just gotta hit something. Not someone — something. You push people to their fullest potential. Who pushed you? —Janessa Hurtig, Froid, Mont. My martial-arts instructor, who worked with me until I was about 21. He changed my life. He demanded ...