You'll need a stability ball for this "Swiss-ball cable Russian-twist" abs exercise from Men's Health. To progress in this particular exercise, simply increase the weight and use a fuller stability ball.
Attach a handle to a high pulley-cable and place a Swiss ball in front of the weights stack. Lie face up on the ball so that the top of your head is towards the weights stack. Reach overhead and grab the handle with both hands, keeping your arms straight and your hips bridged so your body forms a straight line from hips to shoulders.
Turn your shoulders to the left until your arms are parallel to the floor. Rotate back to the starting position and repeat the prescribed number of reps for that side. Next, repeat the move to the right using the same technique.
As you can see, this move is pretty advanced. We recommend you start light and use a softer stability ball, which will roll less as you first get to grips with this exercise. To progress, simply increase the weight and use a fuller stability ball.