PREPARATION
1.Lie on your back with your knees
  bent and feet flat on the floor.

2.Place your hands behind your
  head.

3.Tilt your pelvis forward, so
  your lower back is pressed
  against the floor. Breathe in.

EXERCISE
1.Breathe out as you raise your
  left shoulder and right leg.
  Twist at the waist and extend
  your left hand to touch your
  right foot.

2.Breathe in as you lower your
  shoulder and foot back to the
  floor, returning your hand to
  behind your head.

MAINLY FOR: External obliques