"The things we know best are things we haven't been taught." - Luc de Clapiers de Vauvenargues
Exercise is (or at least, should be) a personal endeavor and to follow specific "rules" often throws a monkey wrench into the works. Too often people handcuff themselves when they use these arbitrary guidelines and because of this, their fitness suffers. They often don't go by "feel" and don't trust what their instincts tell them because certain rules prohibit or recommend otherwise. They don't listen to what their body (physical, emotional, mental and spiritual) needs and their fitness program is lacking - all because of what they've been taught.
It makes perfect sense to seek out knowledge but there is no better teacher then your own experience. Fred Fornicola