You've heard of it. You've done it. Or you're doing it.

Nordic skis are sliding en masse toward next week's American Birkebeiner, the largest race of its kind in North America.

As many as 13,000 skiers will kick and glide and freestyle their way through the weekend events. Most will dig deep for the marathon along the Birkie's woodland trails between the northern Wisconsin towns of Cable and Hayward.

This is as much a story about people as it is about the event. Like so many, Ben Popp grew up with the Birkie. First, watching his parents participate. Then, he did the Barnebirkie kids' races — and on up. Now the executive director of the Birkie Foundation, he knows the event is a beacon that casts a lot of light.

"I think it inspires a lifestyle because it is not only a challenge, but there is a really strong social component to it," Popp said. "And I think you put those two hand in hand, it really is a great equation for creating something exciting."

"If you can enable an experience that allows them to really enjoy it and surround them with a social medium that is supportive — then that only facilitates them wanting to do it more," he said. "And then the more and more they do it, the better they feel. Then, they get their friends to do it. It becomes a self-perpetuating circle."

But any Birkie skier knows the work that goes into finishing the foremost event.

"It's a very unique thing," said Talleiv "Tolly" Vollen, 72, of St. Cloud. "It's just something you have to experience to realize the magnitude of it." Vollen, a veteran of loppets across the world, has skied the Birkie 28 times. Alas, a ski-related injury might short-circuit this year's attempt at 29.

The friends: Bound by sport — and more

Heather Norton-Bower, 42, St. Paul

Birkies: 11

2015: Wave 2, classic

Kitty Earl-Torniainen, 47, St. Paul

Birkies: 15

2015: Elite wave, skate

Margie Nelson, 35, Woodbury

Birkies: eight

2015: Elite wave, classic

Their skiing story is universal and, yet, distinctive. Three women brought together by sport. Three moms helping raise young families and juggling jobs — and fitting in workout time, too. How they reached this point in their friendship as skiing dynamos is where the story leaves the traditional path.

Heather Norton-Bower skied for Minnetonka High School and then a year at Carleton College before she "burned out," she said. Then, four years ago, she rekindled her interest in the sport and began group training.

The closest Kitty Earl-Torniainen got to skis in her young life was watching her sister go off in knickers and high socks, she said. Skiing wasn't on the radar in high school or college. Earl-Torniainen got her start through someone she dated in Madison. By 1995, she was skiing her first Birkie.

Margie Nelson started ski racing as an eighth-grader for St. Louis Park and later competed for St. Olaf College.

Today, Nelson teaches others through Endurance United while continuing to race herself. A little bit of the coach in Nelson comes through when she talks about her friendship with Norton-Bower and Earl-Torniainen. They're top skiers, immersed in the sport, but they are more about "cheering each other on," Nelson said.

"It has to be fun. You have to enjoy it. That's why we do it," she added.

"We definitely push each other. I think we're all rarely feeling intense at the same time," Norton-Bower said. "… Maybe it's not your best workout ever, but [the other two] got you out there. We help push each other in that way. We encourage each other."

That pushing and encouragement comes in group training, the place where Norton-Bower, Earl- Torniainen and Nelson came together.

Norton-Bower said after her first year of group training, a coach recommended she meet Earl-Torniainen. " 'She's super intense,' " Norton-Bower said, recalling the coach's words. " 'You guys would really bond.' " At an end-of-the-year party after a Birkie, the two got acquainted.

"It's sort of a support group slash active activity outlet, so we have as many heart-to-heart discussions as physical things," said Earl-Torniainen, who also coaches in the Minnesota Youth Ski League.

She said the primary impact of their friendship is all positive: they've worked harder, strengthened themselves personally and athletically and they "just have some perspective on all of it."

"I think it is unique to women," Earl-Torniainen said. "I think if you get out with a group of guys, they all want to beat each other. But, women, we all want to talk while we work out. Because that's what we do, and that's what works with us."

Nelson's personal skiing goals mesh with that philosophy.

"Rather than not racing because I'm not going to be as fast as I once was, I try to change my mind-set and make sure I am still out there doing it even though I might not be winning the race or skiing as fast as I hoped. I also like to step back and realize this is something I do for fun to keep myself healthy, to be a role model for my children. So, I just try to remember what I am doing this for."

Like, well, a good boot and binding, the Birkie fits into their dynamic.

Norton-Bower also is now a coach to Endurance United skiers. And, like her friends, the Birkie is circled on the calendar every year.

"I'm slightly obsessed with the Birkie," she said, recounting several early drives in December to Hayward for multihour sessions on the trail before returning to the Twin Cities in time so she and her husband could get their children to their own lessons at Hyland Lake Park Reserve. Nordic fever, indeed.

Earl-Torniainen said she, too, feels camaraderie with the other women she lines up next to at the Birkie.

"I understand the sacrifices it took to get to that spot. … I think our story is reflected over and over."

On skis, battling the winter blues

Dayton Lang, 54, Shoreview

Birkies: three

2015: Wave 5, skate

If bottled, cross-country skiing might be the perfect remedy for winter's long shadow.

Dayton Lang pushes back depression with multihour skate-ski sessions.

Lang is approaching his fourth consecutive Birkie with perspective ("I'll scare no one with my speed") and gratitude. He started small — well, alone — when he got back into the sport several years ago. Then he entered the Vasaloppet in Mora, Minn. Seeing the team uniforms and the camaraderie drew him in. Now, he skis with Endurance United, a St. Paul nonprofit organization that stewards active lifestyles through outdoor sports.

"For me it keeps my motivation up in the winter at a time when darkness just crushes me. I am just really affected," Lang said. "Cross-country skiing is just like manna from heaven in terms of keeping my attitude up. It keeps me positive. And you know the gray, dark winters of Minnesota, so. …"

Even his wife commented on his change in demeanor. Lang recalled her words: "You gotta go out and you gotta go put two hours in this weekend for us and the house. Please, go do that, because you are much more calm and you are easier to be around."

"It was like taking a pill," he said. "It made such a huge difference those years ago."

Then it dawned on him that he wanted to be around other people, rather than watching others together, charged up by their shared sport and activity.

The support was instant and unconditional, Lang said, something innate among the Nordic types.

"Cross-country skiers are nice people, and I think what it is, it's because everyone understands how difficult it is. And they give you credit for the effort."

Ready for his crash course

Lee Rosen, 29, Minneapolis

Birkies: none

2015: Wave 10, skate

Lee Rosen's shift to skiing came on a bike. A new cyclist joined his ride with friends in October, and the chatter turned to the Birkie. "The New York City Marathon of ski racing is what I heard, and I was immediately intrigued," Rosen recalled.

That day, his Birkebeiner story took shape. He immediately registered and, like a snowball with momentum, has continued to pick up the necessities to prepare him for the start line Feb. 21. In December, Rosen hit Gear West for skate skis and went through a "crash course" (as he phrased it) with a friend before signing up for Loppet Nordic racing classes.

"It was just one of those things where, 'This is what I want to do and I'm going to make it happen.' I've always liked trying new things and am up for a challenge."

Rosen had scant experience on Nordic skis. And growing up on alpine outings in Colorado didn't fully translate, of course.

"I've been on skis at 65 miles per hour," Rosen said. "Going down a hill at 25 mph on those [skate] skis is scarier than that. Especially around an icy corner."

Rosen, who moved to Minnesota about a year ago from San Diego, listened to his instructors: It's all about taking small steps. That strategy helped him overcome a steep learning curve his first two weeks. Now, he said, he's focused most on technique and endurance.

Rosen can relate to skiers regardless of ability on one training aspect: Conditions have been at times unkind. He competed in his first race at the shortened City of Lakes Loppet marathon. Last week, the pre-Birkie (42 kilometers) became Plan B for a legitimate test.

An experienced cyclist and road marathoner, Rosen sounded expectant rather than concerned about his biggest race next week. "I know if it takes time I will be able to get through it."

"You do what you know you need to do, and you pace yourself," he said. "Having the experience of long distance races before, you know how your body reacts to certain things."

Battle between father and sons

Talleiv "Tolly" Vollen, 72, St. Cloud

Birkies: 28

2015: Wave 3, classic

Jon Vollen, 45, St. Cloud

Birkies: five

2015: Wave 3, classic

Eric Vollen, 42, St. Paul

Birkies: 13

2015: Wave 2, classic

Nordic skiing always has been the family sport among the Vollens of St. Cloud. Talleiv Vollen, or Tolly, has left a trail of skiing and ski instruction in the community, from organizing morning races for children to opening a seasonal ski store in the 1980s. Son Eric Vollen recalls his older brother, Jon, working at the shop, and both of them prospering in other ways. Their gear, for one, was always top-shelf.

As the years went on, their life stories played out in different ways and in different directions. And all the while, their skiing roots remained deep. Eric recalled returning to the sport after college through Finn Sisu training. Then in the late 1990s he started skiing with his father. Jon, too, had a long hiatus from the sport, lived for years in Alaska, and has now returned to St. Cloud.

"Every year it's kind of a battle of the three. Who is going to be in what place on the medal podium for the three of us," Eric said in jest. "Every year my dad vows to get me next year. The last few years I've been on top with my dad and brother following. … It's more about love of the sport and love of doing it with family."

Tolly recalled "duking it out" with Eric at the Vasaloppet in Mora a few years ago. "He has always beat me," Tolly said, chuckling.

Tolly fell a few weeks ago on a ski outing with Jon in Hyland Lake Park. He might sit out this year's Birkie with two cracked ribs and a sore shoulder. The memories of the Birkie with his family, however, might speed the healing. "It's a special feeling to line up with hundreds of others and your two sons," he said.

"The Vegas oddsmakers have it 50-50 whether Talleiv is going to start or not," Jon said.

" I hope we continue it for a few years," Tolly said. "I'd like to think I can be skiing into my early 80s." Having skied several world loppets — from Norway to points beyond — the outlook appears good.

Said Eric: "There are not many sports that someone can be doing in their 70s and 80s. … For us, it's a lifelong sport, like it is for many."

Jon agreed. "It's just a great tradition, and I hope I am doing it into my 70s like my dad."

A third generation might pick up the mantle. Jon's son Aden and the brothers' niece, Ava, ski the Barnebirkie children's race.

On a glide through life

Chris Sachs, 34, Minneapolis


Birkies: Nine

2015: Elite wave, skate

Who is Chris Sachs? It depends on when you reach him. One day he is the youth ski coach, putting a wrap on another session. Another day, the race director, salvaging a course for a Lake Phalen winter event beset by spring temperatures. He also happens to be an elite skier.

Threaded through these endeavors is his job as executive director of Endurance United (EU), a St. Paul nonprofit centered on getting people active in the outdoors through three core sports, Nordic skiing among them.

From Elm Creek Park Reserve to Battle Creek Park to Hyland Lake Park Reserve and elsewhere, EU's training "bases" are spread across the metro. So are its participants. During any given week in the heart of ski season, there are as many as 17 training sessions across age levels. Not all are training for the Birkie, but many are.

"We have somewhere in the ballpark of 150 to 200 adults training with [Endurance United] in sites around the Twin Cities, and I bet a solid 50 percent of those go and do the Birkie," Sachs said.

EU offers "learn-to-ski" programs for adults, and where those adults take it rests within them. But EU is the binder, and Sachs said transformations can be profound. Some people who have never strapped on skis or maybe get out once or twice a year will go through basic instructional sessions. Then, they are encouraged to move to weekly training sessions. Then, some will think bigger. Maybe the Birkie?

Said Sachs: "We are just as much about supporting each other and creating a community as we are about helping people learn Nordic skiing."

The Birkie is an event that accommodates different nationalities and ages and abilities. Sachs said he wants the same breadth.

"I want Endurance United to be known as many faces, many people. We have people from all walks of life, across the community, many faces that represent our organization. It's an active, healthy outdoor lifestyle," Sachs said. "We want to be inclusive."

Training by night

Joel LaFrance, 34, Plymouth

Birkies: four

2015: Elite, skate

The Birkie will introduce something relatively novel to elite skier Joel LaFrance: fellow racers and daylight.

LaFrance has made a point of training in the margins of the day while he and his wife, Sadie, raise their young family. "It's a lot of working out in the dark, quite honestly," he said.

LaFrance trains five to six days a week once their three children are asleep. His hours are mainly on skis and include multihour sessions. And a headlamp. Sometimes he's on a fat bike or a bike trainer in his family room. Judging from his regimen, he's found success. Last year, LaFrance averaged 11 hours of training a week across seasons. Maybe four or five of those outings, he said, included other people.

That said, Noah, 6, and Gus, 3, know where Dad is off to after bedtime. Three-month-old Ruby will someday, too.

One doesn't have to dig deep to find the source of LaFrance's doggedness. He grew up in a skiing family in Duluth and first heard of the Birkie as a member of the Duluth East High School team. Then he skied for a year at St. John's. He said he took off a decade before "getting back on the bandwagon" in 2011. Positioning himself to teach the sport to his children was a motivator, LaFrance said.

The dueling commitments have shown dividends. The family follows him to races. Gus and Noah learn in the Minnesota Youth Ski League — and during practice loops in the yard. For his part, ­ LaFrance has sights on a top-75 finish in his fifth Birkie.

"It's a religious experience," he wrote of the race in the wee hours of a December morning. "To many, the Birkie trail is hallowed ground. It's a community on skinny skis. The journey from Cable to Hayward is a different metaphor for everyone. For me, it's about competing with myself — seeing how far I can physically push myself. The Birkie is the best proving ground I can think of for that type of competition."

Gophers Nation, too

Karl Holub, 21

Birkies: Two

2015 Birkie: Wave 1, classic

The University of Minnesota Nordic Ski Club might rival some countries with the number of Birkie skiers it's sending north this year. Of the 95 club members, nearly 60 will race.

A major contributor is a $5,000 grant that the club won in a competitive application process, said treasurer Karl Holub. The governing body of the university's sports clubs — everything from fencing to rugby to skiing — awards the money. The club will pick up race registration and lodging for its contingent.

For his part, Holub will race his third Birkie classic. His first, during his freshman year, was in 2013. He bonked at the 40-kilometer mark and struggled in. Last year, he raced smarter, and improved. This year his goal is a top-70 finish and an elite wave qualifier. "You get hooked pretty much after the first one," he said.

Holub, who grew up in New Brighton, first skied competitively in high school after injuries piled up in "contact sports." His low-impact alternative was Nordic skiing. Now a junior at the university, Holub's commitment to skiing is firm — he's overcome two knee surgeries in the last three years — even if his perspective has changed.

Balancing school studies and training is a challenge, Holub said. "The adult world kind of hits hard."

"I still like to think of myself as a competitive skier, but it's definitely harder to have it just be about the races. I do enjoy the recreational aspects of it as well. Just going out there and getting on some trails."

But that adult world has its perks — at least in a Birkie context. Holub, 21, said he is looking forward to his first Jägermeister shot on Lake Hayward a few kilometers shy of the finish.