Being fatigued at the end of your commute not only means you're fat and old and a bad mom, it is the event which has set in motion an inexorable chain of events which will culminate in George W. Bush declaring himself dictator of the Universe, and there will be no election to relieve us of the long national nightmare, and all will look upon you and despair. ...or maybe you just got a hefty dose of tree pollen at May Day, and need more than 2 bike commutes to be back up to speed. :-)