So called ‘slow down’ exercises come from the realisation that for many focal dystonia sufferers, the effects are less pronounced or in fact non-existent at very slow speeds.
From this premise it was suggested to play an excerpt or etude that would normally trigger the dystonic symptoms, but bring the tempo right down to below the threshold where the symptoms kick in. Using a metronome to keep the tempo steady, the idea is to gradually bring the tempo up till the optimum performance tempo is reached.
Rather than increasing the tempo over hours or days, as is probably usual in normal practice routines, this method requires the player to increase only as and when the threshold allows such an increase to be made, and could be over a number of weeks or even months.
The classical guitarist Mark Ashford employed this technique as part of his successful rehabilitation. Naotaka Sakai has done research in this area and outlines the methods and results of his studies in this