Using a Swiss ball during an exercise is a great way to incorporate your core stabilizing muscles, thereby helping your set of dumbbell presses or side lateral raises to also whittle your middle.

Be that as it may, it's important that you don't just select any Swiss ball; the size of the ball should be proportional to your own body size. The perfect ball should allow your entire torso to be supported and in full contact with the ball at the bottom of the move. A larger ball has a gradual arch, so you won't feel as much of a stretch in your abs when performing crunches. A smaller ball, by contrast, has a more abrupt arch, placing your body in a more pronounced stretch position. And, if you're sitting on top of the ball to perform an exercise, you obviously want a ball that's small enough to allow your feet to firmly touch the ground.

So, aside from how you fit on a Swiss ball, you should also take your fitness level into account. As your core strength and flexibility improves, drop down to a smaller size for best results.