Does Size Really Matter?

Actually, yes it does...at least when it comes to choosing the correct stability ball. Most stability balls come with a chart that will tell you what size ball is good for your height, such as this:

Your height Ball size
Less than 5'2" 45 cm
5'2" to 5'7" 55 cm
5'8" to 6 ' 65 cm
More than 6' 75 cm

However, once you get your ball home and inflate it, you want to make sure that it is, in fact, the right size for you:

-Sit on top of the ball (preferably in front of a mirror) with abs engaged and shoulder blades back.
-Check to make sure that your knees are in line with your hips.

If your knees are above your hips, the ball is too tall. However, if your knees are below your hips, the ball is too short. In either of these cases, if the ball is fully inflated, you should exchange the ball for the next size so that you will be able to maintain perfect posture on the ball.