Interesting that you bring it up, as I have, within he last couple of weeks, just joined up with a gym and so far have been gone 5 times each week for about an hour. So far it has been absolutely fantastic...I was never a fat or even significantly unhealthy person, but at the same time I never exercised much save for daily, 45 minute walks (not jogs). Well, I am certainly in a place to appreciate the affect of exercise on one's ability to concentrate, to expel and maintain energy, and just to feel good about himself in general. Even in only two weeks, I have felt an incredible change in all of those traits. Mostly my workouts revolve around cardiovascular activity, as you may expect, such as doing cycling machines and, my favourite, the rowing machines, the latter of which are of course also great for for the legs and torso; however, I also do quite a bit of muscle work, primarily in the stomach, shoulders, and legs--I don't want to focus on building muscle, though, for exactly the reasons mentioned here. I just want to "tone" the muscles a little and make them quicker and easier to control, and also to cut off some of the flab (not like there's a whole lot, but still).
But, my point is I think everyone should have a fairly demanding, though not unreasonable, workout schedule, even if it does just require a 45 minute walk each day...but I think that anyone who has to get on stage and communicate with an audience effectively under stress and so on, should be especially rigorous in his fitness routine, as it should always require an enormous amount of energy, and also self-esteem.