Jessie Diggins could break the United States’ medal drought in women’s cross-country skiing. (Florian Choblet/AFP/Getty Images)

Jessie Diggins is hard to believe, so bubbly it feels forced, so energetic it seems unsustainable. People ask whether she’s fake. She gets that a lot. No one in any walk of life — let alone an elite Olympic athlete in a sport that requires such grueling training for such little glory — can emanate that kind of positivity all the time. Right?

But Diggins, a 26-year-old who is third in the World Cup standings and a legitimate Olympic medal contender, isn’t faking her demeanor. She is working at it, and always has been.

By combining concerted effort to hone her mental approach with a deep commitment to self-exhaustion in her training, Diggins has become the United States’ most recent and promising hope for an Olympic medal in women’s cross-country skiing. No American woman has reached the podium at an Olympics, and her quest to do so will almost certainly begin Saturday in the 7.5 x 7.5-kilometer skiathlon.

Unafraid of questions or cameras, Diggins describes herself with a word rarely used for Olympians not wearing figure skating costumes: “sparkly.” She proudly declares herself the official “cross-country team cheerleader.” Not all athletes would want that title. Not many athletes are as eager as Diggins.

The Minnesota native posts giddy Instagram posts, most with a smile or some inspirational message. She writes paragraphs and paragraphs about positive thinking on her blog. A few years ago, she choreographed a team dance video that involved coaches and technicians. And she has been clear about her priorities: Diggins would much rather her team win a relay than win an individual medal. As admirable as it sounds, the mind-set held her back for years.

As long ago as 2011, when she skied the anchor leg at the world championships as a teenager, Diggins would shine on relay days. She established herself as a clutch skier in races such as those, always able to rise to the occasion. When it came to individual races, her splits were never quite as good.

“On relay days, I would have this superwoman alter ego. I know how to do this,” Diggins said. “. . . I had to transfer that belief and confidence to my own individual races, and learn that it’s okay to care about my own results as much as I care about the team. That was actually very hard for me.”

Diggins worked for that wisdom, spending eight years in contact with a sports psychologist for a less traditional kind of training. Little by little, her individual results improved. By the time she won the 10-kilometer freestyle mass start in her final World Cup event before these Olympics, she was reaping the results of two Olympic cycles of mental and physical training.

“I think she’s figured out that if she can tap into getting those good results on a specific day when the team depends on her, why can’t she just do that when she’s racing for [herself]?” her longtime coach Jason Cork, a member of the U.S. Ski Team’s staff in PyeongChang, said. “She’s worked with some sports psych and stuff like that to just try to figure out how to get focused in on doing that when she needs to do it.”

While individual skiers on the U.S. team are often competing against each other, it’s easy to root for her teammates. She pushes them and they push her, Diggins said. So they share in each other’s successes.

“I’d say like 80 to 85 percent of the time she’s as bubbly as that person, as that person you see on Instagram,” Cork said. “But for sure, she’s definitely human, as every athlete is. . . . Working with a sports psychologist when things do get her down, she’s got a good outlet. And a good support system around her — parents, boyfriend, me — that kind of let her vent a little bit, then get over it.”

With her success has come unprecedented pressure. Only one American has won an Olympic cross-country medal — Bill Koch, silver, 1976. Diggins grew up with a poster of Koch on her wall. It’s still there. But she won’t measure her success her by whether she follows him to the podium.

“For me, the only disappointment that I will actually feel is if we somehow don’t give it everything we have, and if I go out there and race and manage to somehow hold back,” said Diggins, oozing the positivity she’s worked so hard to hone. “. . . I’ve never done that before, so I don’t know why I would [hold back] here.”