Choose a ball chair based on height and quality.

If you are choosing to sit actively, it is important that you choose the right size ball and consider its durability in order to reap the most benefits. To determine the optimal ball size, sit on the ball and look for your thighs to be slightly above parallel with the ground. As you would imagine, taller people will need bigger exercise balls, while shorter people will need smaller ones. Also, make sure you can comfortably sit at your desk, without your thighs hitting the underside of the desk, and without having to raise your elbows too far above your rib cage or reach too far forward to write or type comfortably. To ensure safety, use a burst-rated ball.