Originally Posted by
mr brightside
That's a BOSU ball and it's the best thing for ankle stability exercises, use it stood on the flat side with the ball down. Keep going with it until you can stand on one foot with your eyes closed and with your limbs not flailing around, that's the level i'm at and it didn't take too much work. You need to be at the point where if someone looked at you from the waist up only you'd look like you were just standing there with your eyes shut. I learnt to get on it by gently jumping on and landing with my feet perfectly placed, it adds a new area to work on and challenges you more. You can do delt raises and things too, anything to destabilise you.
Edit- It's key you learn to stand on the thing with your eyes shut. Loss of visual references will boost the functionality of your nervous system a lot over time, depending on how much you practice.