Better Posture
With no chair back to slouch into or armrests to lean on, you’re almost forced to keep your back straight, which can encourage better posture. 

Stronger Core
Sitting up tall forces you to use your core muscles, which not only tones your midsection, but can also help prevent back pain. Remember to actively sit on the ball with a straight back — slouching forward on a ball will not give you a six pack!

Reduced Damage From Sitting
A desk job often means sitting in the same position, hour after hour, but you should be aware that staying sedentary for so long could be lethal. 

Using an exercise ball as a chair may seem easy, but it’s pretty challenging on your muscles since they’re so used to relaxing into a chair.