The Cossack Squat is a great exercise for building strength and flexibility in the hips and adductor muscles. It is a good exercise to work into your warm-up routine prior to working out.
Start with your feet about 2 ½ times the width of your shoulder with your toes pointed outwards and your knees in line with them.
Begin by squatting toward your right side. Slowly move your weight onto your right leg until your left leg is straight, resting only on its heel. Next, slowly shift your weight back to your center and then onto your left leg, repeating the movement. Perform 2-3 sets of 6-12 repetitions on each leg. You will notice that at first you may not be able to go down very far. Just start where you are and try to get a little bit farther with each rep.
Do not lean your body too far forward as this places added stress on the knees. Instead, sit back and use your hips to handle most of the work.