I sometimes use an exercise ball, but that's a dangerous thing to use for long periods of time. Your abs will get tired and you will start to stay in worse posi

I sometimes use an exercise ball, but that's a dangerous thing to use for long periods of time. Your abs will get tired and you will start to stay in worse positions than if you were on a chair. With time, you're able to stay larger amounts of time, but caution is advised!