as you know, piano playing isnt dependent of muscule strenght but of the weight of shoulders and arms. Even more: muscle strenght may decrease the speed. So... why and for whar increase it?Best wishesrui
This particular device I am not familiar with, but generally hand exercise devices are not meant only to increase strength, but also help untighten stiff muscles and increase flexibility. When used correctly they can help with all sorts of unhealthy ways to use the hand and wrist. I used one to get rid of carpal tunnel symptoms.Strength and flexibility are related because the reason behind stiff or cramped muscles is often muscle weakness.
Can't tell if this is crap or might be useful.