Helps with definition.
I love this product, but like all of the door gyms of this nature the bands start to frey in the middles.  They aren't breaking, but I'm not sure when they would.  For the price though and the obvious benifit I don't mind if I would have to replace every 6 months or a year (I use it 4-5 times a week so it's not sitting idle).
Rating: 4 stars