The semi circle exercise on the pilates reformer is a great way to stretch the thighs, strengthen your legs, create more flexibility in your spine and even open up your chest and shoulders. With your feet on the bar and your arms fully extended you lift the hips high up in the air and you will sense a deep stretch in you thighs when the carriage of the reformer is closed to the bar. This position is similar to the yoga pose called the bridge.The as you push the carriage half way out you work the legs against the resistance of the springs, toning your muscles. Then you lower the hips way down where the springs are to get a deep opening in your ribcage,armpits and thoracic spine. After this you return slowly forward and up to the starting position for the thigh stretch. I am always surprised how creative Joseph Pilates was when designing his exercises. He manages to combine stretch and toning of different body parts that work in one organized unit and all of that in a flowing movement that is challenging and fun at the same time!