Anne Frank once wrote "the best remedy for those who are afraid, lonely, or unhappy is to go outside, somewhere where they can be quiet, alone with the heavens, nature, and God. Because only then does one feel that all is as it should be and that God wishes to see people happy, amidst the simple beauty of nature."

As true to today as it was more than fifty years ago, the call of the wild is still alive and well.

Everyone feels it, that tug out the door after lunch, that 'go, go, go" call that pulls at your attention like a magnet. Fresh air invigorates the body like a drug, erasing hours of fluorescent light time in an instant and revitalizing the spirit in ways few other things can. We can't resist it; it's human nature.

As runners, we get out more often than most, but suburban pavement is no substitute for leaves crunching underfoot. Track ash can't possibly replicate the highs and lows of a good run over dirt and rock, and the health benefits that go with it. So for dirt-on-your-shoes, dust-on-your-brow excitement, runners everywhere have to seek out the trails.

The popularity of trail running has grown dramatically in the last decade. So much so that it now boasts an organizing body, the All-American Trail Running Association, has become part of many new triathlon events, and has even been featured in TV and magazine ads. Attracted by new routes, beautiful scenery, and a workout that is a little softer on the knees, runners have been taking up the sport in droves.

But, like many things, transitioning from roads to trails isn't easy. Even seasoned road runners need to realize that the woods present a different set of challenges from the asphalt, forcing the body out of its comfort zone and testing the limits of endurance and conditioning. Sure, the basic form is still there, but on the trail you have roots, rocks, trees, hills, and more competing for your attention. New motions and obstacles attack underutilized muscle groups and challenge even the most seasoned road racer. Make no doubt about it, nature is out to get you and it won't take no for an answer.

Pace
The first thing most new trail runners notice is a dramatic drop off in efficiency, sometimes as much as thirty percent off of their usual performance. This is a normal yet disconcerting part of every trail run, caused by factors ranging from the uneven terrain to changes in the running motion itself. Over time, the body adjusts to running on trails, just as it does to running on pavement, and performance increases as a result. But beginners would be well advised to start slow, focusing on the amount of time they spend running rather than aiming for a set distance, to keep from burning out and to avoid the horribly depressing mileage totals that often occur in the woods.

Why does this happen? For one, running on pavement involves a fairly even back and forth motion, a simple one-two step that lends itself easily to the regular rhythm that many runners rely on. But over uneven dirt trails the body has to compensate for the constantly changing terrain with more of a side-to-side approach. Stopping, starting, ducking, weaving, this motion wakes up underutilized muscle groups all over the body, offering a great workout and making even seasoned racers feel like out-of- shape couch potatoes. Three-mile runs start to feel more like six-mile runs, ten-milers like twenty-milers, with unconditioned muscles responding accordingly.

This uneven terrain also means that a regular pace is next to impossible to maintain. Going up and down hills, tiptoeing over roots, and scrambling around rocks, the body is constantly playing catch-up, something that can make a conditioned runner feel very weak very fast. For this reason, a good trail pace is usually slower than it would be over pavement and often involves walking over difficult passages, something that makes many road- hardened runners cringe. It may feel like cheating, it may seem weak, but periodic walking is just a reality of the trail. Stream crossings, rock beds, heavily rooted areas; these are not places where you should be running. Walk where necessary, be careful, and run again where the trail permits it.

Clothes
Will the usual flimsy running shorts, polypro t-shirts, and, to an extent, road shoes be able to handle the rigors of the trail? In a word: no. Standard issue running gear is designed to be lightweight and wick sweat away from the skin, not stand up to backcountry snags and pulls. This stuff gets torn up when twigs and briars stick to it and rarely survives more than a week or two in the wardrobe of a daily trail runner.

As a result, trail running gear is generally beefier than its road and track counterparts. Heavy nylon shorts, strong polyester shirts, and tighter-fitting garments that will not readily snag on branches make up the bulk of the trail gear on the market, all designed to survive where most other gear won't while still offering the range of motion that runners need. What to look for? Most of the usual rules still apply. Look for layers that will help wick sweat even when dirty, shorts that won't restrict movement, long sleeves to protect from scrapes and bites, and shoes with added support and stability.

Trail shoes are another important item to consider. All the rage with manufacturers these days, these specialty shoes offer heavy knobbed outsoles, tear-proof uppers, and wider designs to promote greater overall stability and increased traction. Traction, stability, and durability are the name of the game when shopping for trail shoes. Look for something with a good tread pattern, to be sure, since that's what will keep your feet from sliding off rocks and slipping down hills, but also be sure it has a wide sole for increased stability and a tough upper to handle the trees and rocks with style. Rigid shoes are a new development, offering greater lateral stability to keep you upright and help protect your ankles from injury, and are something that might work for runners who feel particularly at risk for ankle injury.

Injuries
With its uneven terrain, frequent obstacles, and variable conditions, trail running opens up all sorts of new injury possibilities for runners. The ankles are the most susceptible, as it is easy to step on an unseen rock incorrectly and twist your ankle terribly, but the knees, neck, and lower back are also at risk. Put yourself in the backcountry, miles away from the nearest sign of civilization, and the importance of injury prevention increases tenfold.

One of the easiest ways to prevent injuries on the trail is simply to pay attention. Keep an eye on the ground you're running over while watching out for low-hanging branches and trees. The majority of trail running injuries are caused when runners, not looking where they're stepping, hit a rock or root the wrong way, twist their ankle, and fall to the ground. Not that there aren't obstacles to watch out for on the road, but the trail is riddled with potential pitfalls and will punish the less-than-attentive runner for carelessness every time.

Proper ankle support from a pair of good trail running shoes, a sharp eye, and an understanding of basic backcountry first-aid should be prerequisites for a prolonged trail run. Knowing the terrain and working out with a partner are also good ways to stay safe.

Few things can beat a good trail run; flying through the trees and charging up hills is a running experience like none other. From novices to seasoned pros, the trail is a place to unwind and regroup away from the stresses of modern life, offering a challenging workout that is at once entertaining and fulfilling. While not a sport to be taken lightly, with the proper preparation trail running can be a safe and worry-free experience for runners from all walks of life.

Tim Sprinkle has been running Northern Virginia trails from his home in Arlington for the past four years. In that time, he has only cleaned his shoes once.