The bird-dog resembles the dead bug exercise, but in reverse because you’re kneeling as opposed to lying on your back. However, D’Orazio says that the bird-dog is a slightly more challenging move than the dead bug. “The bird-dog exercise is harder because it requires more balance,” says D’Orazio. “I see a lot more people tilting the wrong way during the bird-dog. They start to lose balance. You have to really use your stabilizer muscles so that you don’t lean to one side.” If you have mobility issues or suffer from severe back pain, start with the dead bug first and build up to the bird-dog exercise.