Many people ask me for a quick and easy way to get core muscles stronger. Of course I recommend Pilates and Yoga, and then I fill them in on a fun and easy way to engage their core all day long.
The greatest aspect of an exercise ball is that you can't slouch on it. If you do, you will start to roll, which forces you to re-engage and sit up straight. It is a known fact that sitting is one of the worst things you can do to your body, but on a ball, you are actually burning calories and promoting good posture.
The ball needs to be a good quality, filled with the appropriate amount of air and also the correct size for your body. Obviously, you need to be the right height from your desk so there is no strain on your upper body when actually working.
The ball is contagious! Once one person in the office has one, everyone wants one, but don't let me convince you. Try it for yourself! Balls range from $25 to $60 so check it out. One word to the wise: Fill it with air AT the office. Not such an easy thing to travel with!
Here is a great article on the dangers of sitting: