"They" say that going backwards on an elliptical, all else being equal, will burn more calories as it is a new postion , and will confuse your body by being somewhat more intense than going forward. Once you get used to it and can do it as easily as going forward, there would no longer be any added value other than it using some of the muscle that you don't use going forward. Mixing it up like that , however, may keep it more interesting just like using different programs on the machine. So the short answer is, go ahead and do it. It can't hurt and might be of some benefit.