THE half a dozen or so trail runners push themselves up the single track trail, darting under a canopy of oak and eucalyptus trees, around burly sage bushes and over slippery stream rocks in Santa Ynez Canyon above Pacific Palisades.
It's halfway into an 8.5-mile run and the sound of heavy breathing and pounding feet grows louder as the runners climb the final incline. The trail veers around a bend and onto a fire road near the ridgeline, giving way to a panoramic view of the blue Pacific, with Catalina Island floating on a bank of fog in the distance.
For an instant, the runners slow their pace to take in the vista -- the big payoff for their aching muscles and burning lungs. "You can hardly believe we are still in Los Angeles," says Annalisa Peterson, a Pepperdine University law student, gazing at the sun-sparkled water.
Runners like Peterson know that, despite boomeranging tree branches, perilous tree roots and slippery stream crossings, trail running is a chance to commune with nature in a way rarely found on cold concrete or blacktop. Running on uneven dirt trails also improves strength and balance in a way that city running doesn't.
These all-natural perks are helping fuel trail running's surging popularity, with the number of trail runners increasing by 26% between 1998 and 2004, according to a 2005 survey by the Outdoor Industry Foundation, the nonprofit offshoot of an industry trade association. With 39.5 million trail runners nationwide, the sport's enthusiasts outnumber skateboarders, boaters, aerobics exercisers and hikers. The sport's coming of age has been heralded by the introduction of an assortment of trail running magazines, trail running shoes and corporate-sponsored backcountry races.
And trail runners are devoted to their sport. The average runner hits the trails nearly 30 times a year, one of the highest participation rates of any outdoor sport, according to the foundation survey.
California's mild weather, miles of shoreline and mountain ranges make the Golden State a hub of trail running. During the recent Santa Ynez Canyon run, members of Pacific Palisades' Trail Runners Club cross paths with half a dozen other regular runners on the mountain trails. They wave, greet each other and exchange gossip like old high school buddies.
In the 1970s, trail running was an obscure sport with few, if any, clubs or organized groups. Some early trail runners were holdovers from high school cross-country teams. In the late 1970s and early 1980s, backcountry endurance races -- including the Western States Endurance Race -- grew in popularity among ultra-endurance runners. The popularity of such races coincided with the nationwide jogging revolution, pioneered by bestselling author and running guru Jim Fixx.
But backcountry running only began to draw big numbers in the mid-1990s, when shoe makers capitalized on the trend by marketing trail shoes with extra insole support and beefier tread for better traction.
Dale Reicheneder, a lifelong runner and national trail running champion, recalls the early days of trail racing when he was among only a few participants. Today, such events attract corporate sponsors and hundreds of top-tier athletes. "The days of showing up and seeing only 20 people in the race are long gone," he says.
Reicheneder, who traveled to 27 cities last year to compete, represents the serious, ultra-competitive side of trail running. For such runners, an 8.5-mile run is a leisurely distance, a warmup before a marathon or other long-distance race. For most local trail running clubs, a typical weekend run stretches 11 to 13 miles, lasting up to two hours.
Still, the sport imposes no mandated minimum distance or speed. Fall back on a long run and most trail runners will wait at the end of the route, offering water, food and encouragement. No one will judge a runner who walks up a steep hill or stops to take in the scenery.
A flexible jog
Trail racers and those who hit the trails simply to stay in shape say that the dirt, leaves and grass give leg joints a welcome break from the punishment endured on rigid pavement.
Several studies back them up, suggesting that running on rigid surfaces -- such as concrete or blacktop -- puts more stress on leg joints than running on softer surfaces.
In a 2002 study, researchers at Harvard University and the Massachusetts Institute of Technology measured the biomechanics of eight men running on surfaces of varying degrees of stiffness. They found that elastic surfaces return some of the energy from a runner stride, increasing speed and reducing the shock suffered by leg joints.
"Running on cement is one of the worst things you can do," says Amy Kerdok, a graduate student and one of the researchers on the Harvard study. "Running on trails, however, dissipates the forces to your joints."