The beauty of abs is that you can work them everyday. I would, time permiting, as this is an easy way to insure 100% on PT for situps. I don't know where you are at physically now, but I know we all have to start somewhere. Know that that is all this is, a start. You will have to do a whole lot more to be a PT stud, which is necessary in the combat arms line of work despite the fact the many have fallen by the wayside. Take it one day at a time, and gradually improve. Up the ante, change up the pace, and avoid monotony on a regular basis.