BRECKENRIDGE, Colo. >> It’s 6 a.m. on a January day, dark as night, and a handful of local athletes are skiing as fast as they can — uphill.

Each of the 31 participants is wearing a headlamp, and nearly all of them are wearing skis that weigh less than an average pair of hiking boots. One of them is Sharon Crawford.

Crawford, 75, who lives in Frisco, Colo., about 10 miles away, is no stranger to uphill ski racing. In fact, she is no stranger to any type of race that involves strain, endurance or pushing one’s body to the limit.

This event, a part of the Breckenridge Ascent Series, took Crawford from the base of the Breckenridge Ski Resort, which has an elevation of 9,600 feet, up a black-rated trail for nearly 2 miles and more than 1,500 vertical feet. The fastest racer, Jill Sorensen, knocked it out in 32 minutes. Crawford clocked in at 1 hour 2 minutes.

“I’ve never had speed,” Crawford, a retired software engineer, said after the race. “I’m more of an endurance person.”

Compared with other competitions in her athletic career, which began in earnest when she was over 30, this race was fairly easy. She has won medals in marathons, triathlons, cross-country ski races, orienteering and multiple-day events. Competitions in uphill skiing, or ski mountaineering — skimo, for short — are increasingly popular and present challenges even for the seasoned athlete.

“When you start getting tired, you think, OK, I’ve got to be ready because the steep part is going to come,” she said. “You have to be prepared to push yourself when you need to.”

Unlike 5- or 10-kilometer running races, which attract a broad range of participants with a broad range of athletic talent, high-elevation winter competitions like the Breck Ascent Series tend to attract superbly fit athletes, many of whom compete internationally.

“You’d think more people would come, but they’re scared,” said Sorensen, 42, who last year won the Xterra Pan American Tour title in the age 40-44 women’s division in triathlon. “Sharon isn’t. I look at her and feel so inspired. My goal is just to last, to take care of my body so I can participate in the sports I love until I’m her age. Not only is she participating, she’s competing.”

Crawford spent her early childhood in Colorado, Arizona and California when her father worked for the Bureau of Indian Affairs. The family eventually settled in Billings, Mont., where she was a Girl Scout, loved the outdoors and pursued interests that were, at the time, dominated by boys.

“All my life it’s been like that,” she said. “I’ve been one of few women. When I was in high school, there were three of us that did physics and chemistry. Women didn’t do sports. Both of my brothers ran cross-country or played basketball. Girls were cheerleaders or played in the band. My father was from an old pioneer family. We’d go fishing and camping all the time.”

Crawford pursued a bachelor’s degree at Stanford and a master’s degree at Montana State before finishing in 1969 and moving to Massachusetts, where she became a software engineer and took up running and orienteering. Her first major event was the Boston Marathon in the early 1970s.

“I needed some exercise,” she said. “The North Medford Club needed women for the old men to beat. A guy started selling shoes out of the back of his car. I bought a pair of Adidas Antelope. I remember running in those the first time I ran the Boston Marathon.”

Crawford became a regular marathoner and competitive orienteer. Upon retiring she moved to Colorado, where her family has deep roots (her great-grandfather James Harvey Crawford founded the town of Steamboat Springs) and where she has continued to broaden her interest in outdoor sports.

Her first uphill ski competition was in Breckenridge in 1996. It was the Imperial Challenge, in which competitors bike or run 6.2 miles from town to the base area of one of the peaks, then climb — either on skis, boards with skins or snowshoes — 3,000 vertical feet to a summit before skiing down to the finish.

Initially, Crawford did the race on Nordic skis with no metal edges. She has worked up to the lightweight ski mountaineering gear she uses today, and also competes in uphill-downhill skimo events like the long-course version of the Breck Ascent Series and the Rando Series at Arapahoe Basin, in which competitors ascend the mountain multiple times and descend on double-black-rated terrain.

When asked about the most difficult aspect of these events, Crawford laughed and said, “Doing them.”

“Waking up early in the morning and being able to pace yourself,” she said. “That’s tough. Then the challenge of the transitions — taking off the skins and skiing down on steep, rough snow on those light skis — that’s the really hard part.”

In such races Crawford is typically among the last to finish, but not always the very last.

“I was born too early for this sport, in a sense,” she said. “In these events there’s no one left in my category. I’m beating some younger people, but not very often. My goal is, can I do as well or better than I did last year?”

Crawford’s schedule revolves around races. In January, a week before the Breck Ascent, she was in Innsbruck, Austria, competing for six consecutive days in Nordic and ski orienteering races at the Winter World Masters Games, where she won five gold medals and a silver.

Recently, she was in Vermont competing on classic skis in the national masters championship, finishing first in her class and significantly ahead of a handful of much younger racers. In February she was in Wisconsin, competing in the classic ski 55-kilometer American Birkebeiner (her 11th of such long-distance events, including the Birkebeiner in Norway). This month she returned to Europe to compete in the Masters World Cup cross- country ski races in Cogne, Italy.

From being one of the few girls in her high school physics class and in the Boston Marathon to becoming the token 75-year-old in an extreme ski mountaineering contest, Crawford has always told herself, “I can do it, too.”

“You have to have your own criteria,” she said. “Sometimes it’s just to participate. In others you want to really be competitive. Now my age group is 75 and up, which is good. I’m going to take advantage of that.”

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