Good Form: Twist exercise works obliques
Your internal and external obliques are located on the sides of the torso. They are responsible for bending and rotating your torso and are used in almost every activity. To train them properly, incorporate twisting moves like this one.
Lie face-up on a mat or a flat, padded surface. Raise your legs straight up and bend your knees so that your shins are parallel to the floor. Place both hands behind your head, elbows pointed to the sides. On an exhalation, contract your abdominals and bring your right shoulder toward your left hip. Pause.
Without allowing your shoulders to drop down, straighten your right leg out in front of you, keeping it a few inches off the floor. At the same time, reach your right arm to the outside of your left leg (still bent). Pause. Return to the starting position, then repeat on the other side. Continue alternating sides until you have done 12 repetitions on each side.