Start by lying down flat on your back and placing your hands lightly on the sides of your head. Do not knit your fingers behind your head or pull on your head with your hands — by doing this you run the risk of straining your neck.
Raise one leg just off the ground and extend it out, and pull the other knee in toward your chest.
Now begin reaching your opposite elbow across toward your opposite knee (right elbow to your left knee, and vice-versa).
As you twist your torso, switch off extending each of your legs, as if you were riding a bicycle.
Perform this movement for three rounds of 20 repetitions.