Neek: Actually, that is a very good question! I have no upper body strength at all but I was still able to use the ab slide. It works out your upper body as well as your abs. When I get done I feel not only my abs getting stronger, but my arms and shoulders too. Trust me, you don't have to be strong to use the Ab Slide.
P.S. The Torso Track is a lot like the Ab Slide except for price. I looked into that Torso Track and figured that it is not worth paying a hundred or so dollars for a machine that does the EXACT same thing as the Slide and is a lot bulkier too. With the Ab Slide it is small enough to put in a closet or in a corner without taking hardly any space.
Well, good luck with your decision.
"A dollar for your thoughts" ~Marilyn Monroe