Of the estimated 1.5 million people who visit Haleakala volcano each year, the most impressive — and confounding — by far are the hale 140 or so who each March take to the 10,000-foot summit by foot.

From Maui Mall. Thirty-seven miles away. For fun.

"It reminded me of my first Ironman," says Wendy Minor, still basking in the endorphin-fueled afterglow of last Saturday's Haleakala Run to the Sun. "It's just mind-boggling to think that I ran all the way up there."

Indeed, ever since local running legend Steve Sobaje first accomplished the feat with two of his coaches some 30 years ago, the Run to the Sun has stood as one of the most robust ultrarunning challenges around.

While relatively short by ultrarunning standards — many of this year's participants have completed races of 100 miles or more — the race offers a degree of difficulty few races can match.

Starting from sea level at Maui Mall, the course cuts through relatively flat Kahului, across rolling hills, up treacherously steep Pulehuiki Road in Kula and finally to the foot of the volcano.

From there, the course winds its way along the mountain's serpentine switchbacks. By the time runners reach the park's ranger station, they've already completed a full marathon, with 10 miles to go in increasingly thin air. It is there, at 8,000 feet, that some runners begin to feel the effects of high altitude.

"I had trouble breathing," Minor said. "I got lightheaded, and I felt like my legs were made of cement. I was wobbling like a drunken sailor those last few miles."

Yet, each year the field is filled with repeat participants, each enamored with the physical beauty of the course, the camaraderie among runners and volunteers, and, above all, the challenge.

MOUNTAINS TO CLIMB

The race is organized by the Hawaiian Ultra Running Team and Valley Isles Road Runners. Even in the best years, the event rarely hits the financial break-even point. But, of course, that's not the point.

HURT's John Salmonson, who works with VIRR's Bram and Joy DeHaan to stage the race, has made personal guarantees to dozens of fence-sitting, would-be participants. Hate the race and dinner at John Dominis is on him. Love it and sweet satisfaction is its own reward.

Salmonson's pride in the race is evident in the litany of runners whose names and stories he can share off the top of his head. This year alone there were Mark Speck, who became the first person to win the race in three consecutive years; Vi Jones, who suffers from ALS but managed to complete the race with a walker; and Paul Sibley, whose recovery from cancer took several steps forward when he made an emotional return to the summit.

And then there was 65-year-old Don Fallis, who started running in his late 50s after being diagnosed with Type II diabetes.

Without having run so much as a 5K, Fallis allowed Salmonson to talk him into doing the Run to the Sun.

"I had a rental car one time that couldn't make it to the top, so I was skeptical and, frankly, scared," he says, laughing. "But John convinced me I could get in shape and do it. It turned out to be a really neat experience. I actually cried at the finish line."

Fallis has now completed the race six times, including once as part of a three-person relay team. (He was recovering from a knee injury suffered when he was on a dog sled in Alaska. Don't ask.)

Thanks in large part to the consistent exercise that allows him to compete in events like the Run to the Sun, Fallis hasn't had to take medication for his diabetes in 10 years. Meanwhile, his list of athletic accomplishments continues to grow, from climbing Kilimanjaro to completing three 100-mile ultramarathons. Next up is a 135-mile race across Death Valley. (Don't ask.)

THE SURVIVOR

Fallis said he was especially gratified to be able to spend time before and after the race with Sibley, whose battle with cancer was felt throughout the ultrarunning community last year.

"It was just inspirational being with him," Fallis says.

Sibley prepared for the race with long hill rides on his bicycle and lunchtime runs from his office on Ke'eaumoku Street up to the top of Tantalus and back. On weekends, he ran 10-mile repeats up Makiki Heights and Tantalus Road and down the Makiki-Tantalus trail system. Sometimes he and his training partners would run around Manoa for a couple of hours before heading up Tantalus, just to get a little tired.

All that training paid off. Not even a year removed from debilitating radiation treatment, Sibley finished the race in seven hours and 58 minutes, nearly half an hour faster than his previous finish in 2004. He'll try to better that time next year.

"It's the only run where you can see the finish from the start," he says. "It's the only one with that elevation gain. When you're on the switchbacks, you can see a runner above you and clouds below you."

THAT SUCKING SOUND

It was exactly 35 years ago that Minor first visited the summit of Haleakala with her family.

"There was not a cloud in the sky and my father said, 'It's a great day to go to the crater,' " she recalls. "It became a family slogan.

"As I got close to the finish line, I started to think about my father and what he would think if he knew I was doing this."

For years, friend Cheryl Loomis, an accomplished ultrarunner, had made it a point to e-mail Minor a Run to the Sun application and every year Minor would delete them. Last year, she finally relented.

The training for the race was enough to convince Minor, already an experienced Ironman triathlete, that she had committed herself to something strange and wonderful. Or, at least strange.

"I remember thinking that these people were nuts," she says. "There we were running up and down these hills, in the rain, at 4 in the morning!"

But Minor was in it for the long haul, and Loomis was right with her, skipping, jumping and doing the hula as they made their way up to the summit.

The two crossed the line together in just under 10 hours.

At the time, Minor thought the race, while greatly satisfying, was probably a once-in-a-lifetime deal. But that didn't last long.

"They told me that this race will suck you in," Minor says. "And two days later I could hear this sucking sound. It was sucking me in. I heard a voice in my head saying, 'I can do this faster.' "

But that's next year.

"Now I'm going to go back and do something simpler," she says, "like the Ironman."

2007 RUN TO THE SUN WINNERS

SOLO

Men: Mark Speck, 5:55:37

Women: Sara Clark, 7:00:21

TEAM

Men: Upcountry Fitness (Mike Irwin, Dagen Bendixen, William Turner), 5:21:20

Women: Crater Climbers (Julie Rohde, Karen Love, Lindsey Wilber), 6:35:59

Mixed: Haleakala Hustlers (Kevin Davies, Ariel Salinas, Kristy Rice), 5:56:26

Reach Michael Tsai at mtsai@honoluluadvertiser.com.