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

2.Tilt your pelvis forward, so
  your lower back is pressed
  against the floor.

3.Place your left hand behind your
  head. Place your right hand on
  the front of your right thigh.
  Breathe in.

EXERCISE
1.Breathe out as you curl your
  shoulders away from the floor,
  reaching your right hand along
  your thigh, towards your knee.

2.Breathe in as you lower your
  shoulders back to the floor,
  returning your right hand to
  the start position.

Do not to relax your abdominals
between repetitions.

MAINLY FOR: Rectus abdominis

To make the exercise more
demanding, try to reach your right
hand beyond your knee.