Start by lying on the ground, with your lower back pressed flat into the floor and your head and shoulders raised slightly above it. Place your hands lightly on the sides of your head; don’t knit your fingers behind. Be careful not to yank your head with your hands at any point during the exercise. Lift one leg just off the ground and extend it out. Lift the other leg and bend your knee towards your chest. As you do so twist through your core so the opposite arm comes towards the raised knee. You don’t need to touch elbow to knee, instead focus on moving through your core as you turn your torso. Your elbow should stay in same position relative to your head throughout the turn that brings it closer to the knee comes from your core. It might be best to think shoulder to knee as you move, rather than elbow to knee. Lower your leg and arm at the same time while bringing up the opposite two limbs to mirror the movement.