Breathing while engaging corset

We don't believe that you should try to restrict the breath anywhere. (For a few purposes, like singing or playing an instrument, it is useful to be able to control the breath, and you do have more control when you are belly breathing - so that's the one exception.) When the chest is open because you have good architecture and your shoulders' default position is open and back, breath will be able to expand into the chest. You should not feel like you have to force the breath anywhere. Consider the fact that when you are doing something demanding, like exercising, it is crucial that you use your inner corset to protect your back. And the inner corset involves those deep muscles in the abdomen (such as the transversus abdominis) that essentially create a taught canvas over the belly and thus restrict how much you can breathe into the abdomen. But you still need to breathe when you are exercising! In fact - you need MORE air and oxygen when you are exercising that when you are at rest. So your chest absolutely needs to be able to move and expand so you can still get air in those situations. One other note - in my experience (and Esther's), people who have spent a lot of effort trying to breathe only into their bellies tend to have weak abdominal muscles.