You think nurses run around none stop or something? Nursing isn't really an exhaustive job (for the most part). You don't do anything to exert yourself really.
Ever worked a 12 hour shift on a ward? Until then, kindly, shhhh. Nurses do nothing but run around non-stop, yes your not hauling bags of cement, but when you have spent your shift repositioning bed-bound patients, washing people and wiping bottoms, I would rather the cement. Its just that most nurses choose not to complain about it, its the job you choose. Try reading this, its a pretty accurate post
http://ernursey.blogspot.com/2007/09/typical-day.html