I've always found that standing does something to your energy level, those who stand tend to sound more "up". It has also been my experience that standing also takes away from concentration slightly, some people get a little more nervous standing vs sitting. In the days of 3 hour jock shifts, one could stand the whole shift and be energetic. Today with live shifts often 4, 5, or more hours, it's a bit difficult to be on your feet that long.