Lie with the ball resting under your left armpit, with your left leg folded underneath you. Hold the dumb-bell in your right hand at arms length in front of you, level with the floor. Without bending your arm and keeping the ball steady by contracting your core, bring your arm up above you in line with your shoulder so that it is almost vertical. Pause and then lower the dumb-bell back down again. Do ten reps then switch sides and do another ten.