One day, Folsom ultramarathoner Erik Skaden was on a long training run with fellow ultra elite Tom Johnson. The two usually have plenty to chat about while tearing up the trails, but this time Skaden was quiet.

Forty minutes later, he finally spoke.

"I told him, 'Hey, sorry about that. If you were speaking to me, I was at the beach for the last six miles,' " Skaden recalls. "He says, 'That's OK, I checked out, too.' "

Skaden had experienced what psychologists call "dissociation" and what most long-distance runners simply call "spacing out." The longer the race, the more you'll find athletes using this mental ploy to mask the pain and blot out the monotony by thinking about anything except the task at hand.

For those watching Saturday's Western States 100-Mile Endurance Run and wondering, "What the heck do these people think about?" it could be anything from visualizing themselves lounging in a cool stream to fixating on the gorgeous views to chanting mantras under their breath.

Then again, the runners could be doing the opposite: doing mental inventories of their various body parts, checking time splits, gauging when to refuel with electrolytes and caloric intake, and deciding where along the course to put the hammer down and push.

This latter thought process, called "association," is especially true at the front of the pack, where staying highly focused on the task at hand can be key to a top performance.

Elite athletes such as Skaden, who finished in second place in 2007 and was the 2008 co-champion of the USA Track & Field National 100-Mile Trail Championship, use both mental tactics to their advantage.

"You can't disassociate for 16 hours, but you can periodically escape from what you're doing at the moment," Skaden says. "When you're in the flat sections (of the Western States course) where it's monotonous, that's when you dissociate."

The advantages of dissociation are obvious. One's body is put through a lot in an ultra race, so distractions from pain are welcome. Then again, you can dissociate yourself right out of consciousness.

In the 2006 Western States, Seattle's Brian Morrison, on his way to victory, collapsed just before the finish line. He was helped across but ultimately was disqualified. He says he still doesn't remember what happened.

Morrison's is an extreme case. But even those as experienced as five-time Western States winner Tim Twiet-meyer say they give their minds a break during the hours on the trails.

"There's got to be times when you've got to pay attention to how you're going," Twietmeyer says. "It's a constant calculation. But early on, (dissociation) is definitely the case.

"It's such a long race. At mile 2, if you're saying, 'OK, how hard should I run,' by mile 30, you'll be going cuckoo. Early on, you know you have plenty of gas in the tank, so you can check out occasionally. But later on, it gets pretty serious."

Even at the shorter distances, such as marathons (26.2 miles) and half-marathons (13.1), selective dissociation can help many runners, especially the non-elite facing the so-called "wall" late in a race.

But if you want to go fast, research suggests that runners try to associate as much as possible.

An early study on dissociation, published in the journal Cognitive Therapy and Research, looked at the mental race strategies of 32 male participants in the 1988 Olympic Marathon Trials.

Higher-placing runners reported using association more regularly over the course of the race than did lower-placed finishers, who adopted dissociation early in the race (5 to 8 miles). Faster runners say they segued between the two mental states over the first 18 miles.

In 2006, a University of Minnesota-Duluth psychology professor gave a questionnaire to 300 participants in the Grandma's Marathon. The professor, Rick LaCaille, told Runner's World magazine, "People who were internally associating were more likely to hit the wall than those utilizing the other strategies." He theorized that recreational runners aren't as adept at "problem-solving" physical problems as elite runners.

Call The Bee's Sam McManis, (916) 321-1145. Read his postings on the "Sacramento Health & Fitness" blog at sacbee.com/blogs.