I agree with Smrobs. I am highly resentful of excersize because I am slightly lazy and non-athletic, but I'm still in good shape from riding all the time. Posting actually works in sort-of the same way jogging does.....Eh. Sort of. Works good enough at least
I also have difficulty because of my disability. Working does keep you fairly in shape, if not through loss fat through gain of muscle. One thing I highly recomimend AGAINST however is jogging. Ellipticals and such should be fine, but I wouldn't do any sort of impact exercising because it'll screw your knees up.