So, trail running versus road running. There really isn't much difference is there?
At the base level, not much. Running, sweating, hydration, fatigue. They all come into play on the trail as much as the open road (or sidewalk as the case may be).
I have tons more experience running on a flat, paved surface than a sandy, root filled trail. However, I have completed a few trail runs this year (one race, two training runs) and there are a couple of things that have jumped out at me, both literally and figuratively, that is different.
Intensity. A good trail (defined here as containing slopes, loose sand, low hanging branches and high arching roots and maybe a river or two to cross) demands much more total and immediate concentration. You simply cannot lapse into that "runner's coma" like you might during a long road run in familiar territory. The moment you start thinking about Aunt Petunia's apple pie is the moment you get lashed across the face with a low hanging branch or step on a sand colored rock twisting your ankle. You must concentrate. And you must do this from start to finish. You don't realize how much effort it takes to focus on each foot fall until after you're a couple miles in and fatigue starts affecting you as much mentally as physically.
Conditioning. It's a lot of work weaving through a forest trail and over terrain in which your foot slips a bit on each step. This seems obvious but it did catch me by surprise. I run marathons, right? How hard could 10 mile trail runs be? Answer: Pretty exhausting. There are a bunch more muscles that come into play to stabilize your knees and ankles as you bounce across the uneven trail to basically keep you upright. Count me as someone a bit naive to this. I nearly collapsed my left ankle about a dozen times during the 10 mile race I did. I just wasn't used to the need to balance while running. I'm currently paying the price for this lack of strength in my stabilizer muscles. My left ankle muscles (ligaments?) have been sore for 4 weeks. The outer edge of my right knee is sore since the Higgins Lake trail over a week ago. So much so that I still have a slight limp during regular walking this week. I'm finding it hard to keep up playing soccer and basketball with my kids in the yard as the side to side motion is killing me. Thank God Chicago is flat...and paved.
Fun. Though it's a bit more grueling, I've really enjoyed the few trails I've ran and hope to do more. I'm currently scouting for a pair of good trail shoes. It's fun to become "lost" in the trees hearing no one ahead or behind you, wondering where the trail ends, only to emerge into a open field and parking lot. There's always a new challenge around each bend....loose sand, a rock strewn path, an unexpected hill. It keeps you on your toes. There is a feeling of accomplishment when you've completed a difficult trail run.
Plus, it's just a nice change of pace if regular road running has grown a bit routine. Try it!