If you go through the same postures all the time, your body will become so accustomed to doing them, they'll seem easy, which means using less energy to do them. Challenge your muscles by trying out new or more difficult poses to place new demands on your muscles. When you feel your arms and abs shake in an arm balance like Headstand B, you'll know you're working hard and burning more calories in the process. Obviously only do poses you're ready for, being sure to ask your instructor for safe ways to approach them.
Source: Louisa Larson Photography