Also while on the last one, get near the ropes with your Hand on the top rope. Now start bouncing with your knees on the Ball, then jump and stand on the Ball very explosive. You will fall arse over Tit a few times, but with the Hand on the Ropes its pretty safe, great for explosive Balance and Speed. Another one whose ever tried punching a Fit Ball against a Wall and keeping it up it takes Speed and good Technique and fast Feet .