I'm going to show you how to do knee tucks on an exercise ball. Okay. What you're going to do is, you're going to lie down on the ball in like a front [recline] type position but your feet are going to be on the ball, so it takes a little bit of balance. It's a great exercise for the core and your upper body, just to get some stability.
Notice the ball's right around my knees, the ball is resting on my kneecaps and I'm going to drive those knees in to my mid-section so it really hits the lower abdominals in this exercise. Exhale when you bring the knees in, okay, extend back out. Remember, try not to rest very long because you want to keep that resistance on the lower abdominals. You're driving both knees in together holding for about a one count at the point of contraction.
Okay. Keep the shoulders in line with the hands for your upper body's positioning. That's how you properly do a knee tuck on an exercise ball.