Because you are lying supine (face up), this exercise biases the muscles on the back of your spine, back of the pelvis, back of the legs and back of the shoulders: hamstrings, glutes, posterior deltoid, etc.
Start with very short movements and always return to 12:00 and pause to regroup and feel in control. This can be considered a beginner exercise if only short movements are attempted.
This is a great exercise to work on if you are trying to prevent back pain. It forces you to use muscles that are often inhibited as we sit at desks all day. The scapular rotators, rotator cuff, posterior deltoid, back extensors, and the gluteal muscles are often underused in most sedentary occupations.
A lot of more advanced exercise ball exercises start with this position.
Knee Pushup on Ball
This exercise is easier because you are on your knees; however, it is a challenge to your scapular stabilizers.
Work your glutes and lower back extensors with this ball exercise.
Bilateral Leg Raise with Hands on Hips
Here's a challenge to your balance and pelvic control. You may want to start this one with the ball up against a wall.
A good exercise for pelvic stabilizers, quads and glutes, always make sure your knee doesn't move in front of your foot.
Here, hip extensors and abdominals work together to maintain a stable core.
The little added weight of the exercise ball makes this a challenge to your abdominals to maintain neutral spinal positioning.
Floor Ab Crunch
Simply another way of performing the standard "crunch" that everyone knows and loves.
Calf Raise 2
Leaning forward with the ball doing this exercise works your calves through a different range.
You'd be surprised at how weak your scapular stabilizers are. Try this without allowing your shoulder blades to move or stick out.
More scapular stabilization.
Squats are great for hip strengthening- often one of the weakest links.
Go back to the basics
Another beginner exercise ball workout
An intermediate exercise ball workout
Another intermediate exercise ball workout
No time to exercise!
To review ball exercise workout safety: