If you've ever walked by Funky Door Yoga on Shattuck Avenue in Berkeley, you may not have guessed that those human pretzels glazed with shiny sweat, baking in 105-degree heat, are burning nine hundred calories with their workout. Maybe you've always wanted to try yoga -- maybe you like it but need that extra oomph of a challenge -- or maybe you think of it as just the kind of Berkeley mumbo-jumbo you'd prefer to steer clear of. In this room of hot-crossed buns, though, lies a serious workout with tremendous benefits. Participants of all levels in shorts or swim attire are guided through 26 poses during ninety minutes in Bikram Choudhury's copyrighted "Bikram" method of hatha yoga. Helpful, highly trained instructors lead six or seven classes a day that accommodate almost any schedule. Part of this exercise's charm is sweating with a roomful of almost-naked strangers while everyone's muscles relax and stretch farther with the heat. Bikram is a learning experience, too, as instructors spell out which internal organs are being massaged and twisted, tissues and joints revitalized, and what far reaches of the body are getting fresh blood. Your chakras will love it. The experience is infused with the same humor found in the flamboyant paintings of yoga poses around the studio done by formerly local artist Ed Renfro. The mere act of staying in the heated room for ninety minutes is beneficial, and the experience dramatically improves after the first visit. Behind the funky door is a great way to whip your body into shape, and guess what: You'll burn hundreds of calories along the way.