The course I went on lasted for three days. Within a day I was starting to feel the benefits. After three days I could get a real sense that this could work for me, I could pretty much say anything. The mentors on the course were also a great inspiration and drove me forward to keep focusing on the technique. Over the coming months I had a few dips in my speech, but in general my control became more confident. Over a short period of time the breaths I was taking became less deliberate and obvious and my speech rhythm was assimilated into my new pattern of speech (I was delighted to leave behind my stammering pattern of speech!). I have now been using costal breathing for 22 years and life has been brilliant with calm and controlled speech. I haven't done another video referencing the mechanics of how the technique works. I'd say if you believe it can work it can, the 1000's who have benefited are testimony to this. What is also important is to get involved with a stammering community that believes in costal breathing to give you support during the peaks and troughs of recovery.