There is a fascinating piece in the Telegraph about a course that cures stammering:

In August last year, I attended my first session of the McGuire progamme, an experience I can only describe as liberating. The main focus is on learning a technique called "costal breathing". It involves using a different part of the diaphragm – the muscle below the lungs – to generate a deep, full breath, generating the power to push out the words.

What makes the programme distinctive is that it is a speech therapy course run for stammerers by recovering stammerers. This creates a sense of honesty and trust: everybody in the room knows everybody else's biggest secret.

At the end of each course, all the students make a speech in front of hundreds of people. Difficult enough for most non-stammerers, this is a test of nerve, composure and technique. When I stepped down from the platform, the feeling of elation – the freedom of finally being able to express myself fully – was overwhelming.

This is how singers and woodwind players are taught to breath, if I am not mistaken.

Link to the McGuire Programme website here.