When I say Bikram Yoga is hot, that's quite an understatement. You don't know how hot it is until you set foot in a Bikram studio. It's like walking into a sauna. The room is heated to at least 40°C and 40 percent humidity. The extreme heat is meant to encourage your muscles to open up quickly, so you're able to get deep into poses.A 90-minute Bikram yoga class burns 1000 calories per class.