Use a light to moderate weight for the first time you do the exercise. Grab both handles then stand in the middle between the two stacks. Bring your arms up so that your arms are bent and your fists are only a couple of inches apart and held out in front of you:

Don't press your hands together - keep them a little apart through the whole exercise. It's this non-pressing together that keeps the tension on the deep abdominals while simulataneously taking the torque off the lower back by balancing the forces between the two sides.

Now rotate to the right, keeping your arms pretty much in place. A little movement is okay but it's a not a full pressing type of movement. The movement should come from your core.



It may seem like the two opposing forces take tension off the abs but because you're holding the cables out in front of you, the tension does stay on.

Now come back around to the front:



Then rotate to the left:

Repeat for as many reps as you can do. If you can get more than 10 reps, increase the weights next time.

You can also do this exercise somewhat explosively, adding some powerful rotation into the mix rather than the more deliberate movement. This works well with the balanced torque on the body - reduced possibility of injury even when doing explosive rotational movements. This method is also shown on the video below.