They also have a tread that looks like a knobby tire with rubber as sticky as rock climbing shoes. I'm of the ilk that if you run in the hills enough, in time, those muscles will strengthen. Unlike Mr. Carpenter, I do not enjoy catching a stone on the ball of my foot through my shoe. Having a shoe specifically meant to run wild in will probably prove advantageous. Most are still amazingly light and versatile, able to carry you over any paved running you have to do to hit the trails.
Water is an important consideration when on trail.
While most runs are no more than an hour or two away from civilization, the Unknown is always a fellow trail runner. There are fanny packs that have space for one or two water bottles on the waist strap. I recommend the double shot kind for added liquid carrying capacity. The latest gear in drinking water on the fly is the bladder-type hydration systems, two brand names being CamelBak and Platypus. A long tube allows for hands-off draughts of this precious fluid.