Believe it or not speaking takes a lot of energy. Many people have said that some of the greats lik Zig Zigler and Tony Robbins walk back and forth across the stage to the tune of 10+ miles during a presentation.
That is just the presentation!!! Now add in preparation, rehearsal, travel...etc. It takes a serious toll on the body.
So be sure to take care of yourself. Eat a balanced diet, even on the road. Get regular exercise. Meditate. Take a day of rest after a presentation to decompress.
With the energy required in this industry, taking care of your physical and mental health is imperative!