Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Deflated.

I borrowed this from someone, box unopened. (They received it a couple of months ago.) At first, I thought it was a good alternative to a fitness ball because of its stability. I was able to do many exercises that I can't perform on the fitness ball, for example the "Superman," and I figured it would be a great way to build up to more demanding exercise. Plus, I hate getting down on the floor to do ab exercises.I was even considering buying the deluxe version. But in less than two weeks,it's gone completely flat. By contrast, my fit ball, which was filled well over a year ago, is a little squishy, but still perfectly usable.