oh my goodness, why did they say that? Ramp up your system before you exercise???? That makes no sense!
For exercise to be productive, you have to be able to breathe thru your nose the entire time. If you get to the point where you absolutely have to breathe thru your mouth, then you've reached the point of adrenaline-induced breathing, which means you're no longer producing energy, you're instead draining energy reserves including hormonal energy. Adding caffeine to the mix would mean that your adrenals will shoot out more adrenaline. That's draining, not rebuilding, and means very slow recovery times.
Ideally, you should exercise to the point where, once you stop and shower and get dressed and rest for 15 minutes, you feel like taking on the whole world! :)