Pick a mountain range, measure off a 100-mile trail and then find out who can run it the fastest. That's the sport of ultramarathoning, but why would someone want to do it? "I call it fast backpacking," laughed this week's subject John Hallsten. "I can go a hundred miles in a day."

Hallsten (pronounced hall-STEEN), 51, has completed nine 100-mile runs so far in his career, and has no plans of slowing down.

He recently won his third age-group championship at the HURL Elkhorn 50-mile Ultramarathon. Hallsten traversed the distance through the Helena National Forest in 10 hours, 48 minutes, winning the grand masters race (50-59 years) and placing fourth overall.

He started out running cross country and track for Missoula Hellgate in the mid-1970s. After a year of college at the University of Montana, he began competing in the annual in the 10K runs in Missoula, before relocating to Helena in the mid-1980s, when he started running in the Governor's Cup.

In about 1998, Hallsten met Martin Miller and Steve Engebrecht of the Helena Running Club. During their training runs together in the south hills trails, the two men talked him into running that year's Elkhorn 50K, and he's been hooked on ultramarathons ever since.

Hallsten's very first 100-mile run was the Cascade Crest in Washington in 2000. Since then, he has finished eight other 100-mile races, including what's considered the king of them all -- Colorado's Hardrock 100 Endurance Run. He has completed two Hardrocks, in addition to serving as a pacer for Miller in another. His best time for the punishing event was 34 hours.

Hallsten has gone under 24 hours in three different 100-mile runs; the Bear 100 in southwest Idaho, the Western States Ultra in California, and the Leadville (Colo.) 100. At the time he completed the Washington Plain 100 -- which has only one aid station, halfway through -- he was only the seventh person to do so.

Hallsten's goals this year are to run in six Montana ultras: the Fat Ass 50K, the Old Gabe (Jim Bridger) 50K, Devil's Backbone 50-miler, the Elkhorn, Swan Crest 57K and the Le Griz 50-mile.

Ultramarathoners sustain an inordinate number injuries and are exposed to extreme temperature variances. Hallsten has experienced his share of maladies over the years while competing, including a torn Achilles tendon, a cracked rib and a twisted ankle. During the grueling Wasatch 100, he suffered through dehydration, heat exhaustion and hypothermia, all in the same day.

"But I have never not finished a race," he said proudly.

Q How often and how far do you run for training?

A Hallsten: I usually run every day, except after a race. And I'm running about 50 miles a week now. I'd like to do 70 but it's hard to find the time.

Q What goes through your mind during the 30 hours of a race?

A Hallsten: Well, there are a million things to think about, like friends and family. But most of the time you're concentrating on what your body is doing, and monitoring what you think it needs next, like water, food, rest, etc.

Q What are some of your hobbies?

A Hallsten: Hunting, fishing, the Boy Scouts and Montana Grizzly football.

Q What keeps you running ultramarathons?

A Hallsten: I've always been adventurous and I enjoy the challenge.

Q What is the highlight of your career?

A Hallsten: I think the most pride I've felt was finishing those two Hardrock 100s. That's one of the toughest things in the world. And I remember the exhilaration I felt when I crossed the finish line in that first Cascade run. I was driving home on the freeway the next day and I just yelled out, "I did it!"