This exercise, the plié, is borrowed from ballet. It is one of the fundamental exercises taught in ballet. It is excellent for strengthening and elongating the inners thighs, the pelvic floor, and the gluteus.
It is different from a squat. In performing a plié, you must keep a well-aligned upright posture throughout the entire exercise. By doing this, you will feel the entire body working.
Prepare by standing with the feet shoulder width apart and parallel to each other. From the root of the thigh (where it inserts into the hip) rotate the thighs externally. This will turn the feet out. Many people make the mistake of turning their feet out from the ankles. The ankles usually have more external rotation than the hips joints do, so we must rotate from the hips to insure that the knees will be properly aligned with the feet. Otherwise, we are setting ourselves up for injury.
After externally rotating the legs, draw the pelvic floor up and pull the inner thighs toward each other. The buttocks will naturally engage, however be sure not to tighten it so much that the pelvis tucks under. This will have a shortening effect. You want to feel the base of the gluteus engaging to help you lift up.
Press the heels down toward the earth and lift the front of the hips. Draw in the navel, keeping the lower back strong and maintain its natural curve. Press the shoulders down. Keep the shoulders broad and open. The ears remain aligned over the shoulders. The neck should feel free and light. Imagine lengthening the two sides of the neck.
Hold a weighted medicine ball in front of the lower abdomen. Slowly (take four counts) bend the knees into a deep plié. While executing the plié, keep pressing the knees open, so they remain in line with the toes.
As you plié, do not allow your energy to drop. Keep lengthening up your spine and send your internal energy toward the sky. What often happens when people try to do this is that they jut their ribcage out. Keep the chest relaxed and the ribs down in the front of the body. In Pilates, they often cue one to knit their ribcage together. You may think of knitting them together, but avoid squeezing them together. You should be able to breathe well.
As you rise, press your internal energy down toward the earth, and pull the inner thighs toward each other.
Repeat this four times.