Rest your feet up on a flat bench and grab hold of an exercise ball on the opposite side. Your neck, back and legs should be in a straight line (it's OK if your legs are bent slightly at your knees). Your arms should be extended but not locked out and to the sides of the ball. This is your starting position.
Lower your upper body down to the exercise ball until it touches the ball. Then, raise your upper body back up to the starting position. Repeat the movement for the desired number of repetitions.
Perform this exercise in a smooth and fluid motion
Maintain proper balance at all times
Don't lock out your arms at the top
SPECIAL NOTES & LEVEL of DIFFICULTY VARIATIONS
To increase the level of difficulty, slow down the movement or have someone place a weightplate flat on your upper back.