Walking out/Plankng and front of the U

I did the walking out/planking exercise. I forget the correct term. After I went back to the standing meditation when I would do the pitcher breath it felt like the top front of the U was getting a big stretch even though I was trying to breathe and fill up the pitcher from the bottom. Is this part of what is supposed to happen as a result of the planking? I also noticed that the toes felt different. I didn't feel the pull underneath the feet like I felt the first time when we practiced this but maybe the toes feeling is related.