There's a reason everyone--from patchouli-scented hippies to straight-laced CEOs--is flocking to yoga classes: They work. But if you're still daunted by the idea of bending yourself into a pretzel while balancing on one foot, you may take a liking to one of the newest yoga styles. Forrest yoga focuses on breath work and core strengthening. But Forrest yoga, named for yoga guru Ana Forrest, is no walk in the park. "There is sweating involved," said Steve Emmerman, an instructor at new Nirvana Yoga and Massage. "This is not a sleepy yoga." Nirvana offers two Forrest yoga classes a week, as well as more traditional styles, including hatha, ashtanga and Kripalu. Prices range from $12-$15 for a 60- or 90-minute yoga class to $150 for unlimited monthly classes. 222 S. Morgan St. Suite 3C, 312-829-9642.