Woodchop

This exercise works all abdominal muscles.

Stand with your feet a little wider than shoulder width apart and keep your knees slightly bent.

Keep your arms overhead almost straight.

As you exhale, pull your abs and arms across your body toward your right knee (as if your  you're chopping some wood).

As you inhale return to the starting position.

This exercise isn't recommended for people with torso injuries.

To work oblique muscles better, keep the angle of 45 degrees when you bend.

You can use a dumbbell or a ball as an additional weight.