Normally in German you tell someone „Hold your breath”, to make him finally shut up. That it’s also possible to train the abdominals therewith was new for me. But, because it’s very strenuous I think it could work out. It’s worth a try.
I crouch down on the floor, take a deep breath and move my belly as far as possible backwards and up. Now I have to hold the breath and also the tense in my belly area. It’s no so easy! Then I breathe out slowly and repeat the exercise after a few breaths.