We all know that once we have established some kind of workout routine, it is necessary to switch it up every few months and challenge us again, so we don’t get too used to it and stop seeing results. Now with all of us knowing that and nodding our head in approval, I come to wonder how many of us actually do it? I have to admit I am guilty of sticking to the same set of reps for ages, only reluctantly adding weight or, god forbid, even changing my playlist. But to…