Has anyone tried Costal diaphragm breathing

Has anyone tried Costal diaphragm breathing Recently, I was reading "Beyond sttuttering" by Dave Mcguire. In his book he has mentioned that those breathe with costal diaphragm achieve more fluency & eloquent speech. The book stated that it's a very effective and an initial start to achieve fluency. I have just started it out. Any tips??? Or you can share your experience if tried.