First of all, I didn't make up the name, but this is still a great mobility exercise to use. Imagine a spinning ballerina with one bent leg held up. The position of the leg in this exercise is the reverse of the leg position the ballerina would hold. This technique will help you mobilize the tissue above and below your hips as well as the adductors.
Working on your adductors will help improve the position of your pelvis in the bottom of the squat. If they are too tight you will likely suffer from the dreaded butt wink and have difficulty driving your knees out when squatting.
Reverse Ballerina Hip and Adductor Stretch
IMPROVES: Hip Extension, Hip Internal Rotation, Flexion and External Rotation
TEST: First test for butt wink at the bottom position of the squat. You may need a partner to check it out for you.
1. Put your right foot at the corner or far edge of a box.
2. Place your right knee, shin, and ankle on the box and turn away from your right leg.
3. Push down into the box with your right knee as you continue to turn away.
4. Search for more stiff areas by lowering your body as you twist.
You may be able to get a little more by stretching your right arm over your head while you continue the stretch.
Be sure to apply this to both legs.
Occilate in and out of tension in positions 3,4 and 5 to gently encourage the tissue to loosen up. You can also use the contract / relax technique over any tight spots - Contract your legs while you count to 5, then relax deeper into the position. Do this for a few rounds until you feel the tight spot release.
RE-TEST: Test your squat in the bottom position again. Can you drive your knees out? Can you maintain a neutral position with your pelvis as you get low?
How was it? Let me know in the comments below after you try this exercise.
Credit: Becoming a Supple Leopard, Kelly Starrett MobilityWOD.com