The Ironman Triathlon consists of a 2.4-mile swim, 112-mile bike ride and a 26.2-mile run. Surely, one might think, such a feat of athleticism would explode the joints of a human over, what, 40?

Not so, at least for the super-human. Mariana Phipps will be 71 this coming May. She’s a mom to three boys. Heck, she’s grandma to six children. Yet, she’s still a top competitor in one of the world’s most grueling test of human endurance.

Phipps was a swimmer as a girl, but couldn’t compete in high school or college in pre-Title IX days. By the time she started taking classes at Creighton University, it seemed that her serious days as an athlete were behind her.

“I was a pretty good, heavy smoker, and didn’t even think about doing any sports,” she says. “I had kids and I was busy.”

When her husband found out he had heart disease, they both quit smoking. However, she says, when you quit smoking, you need to do something else, “otherwise you blow up pretty fast.” She got back into swimming, and since many of her fellow swimmers were runners as well, she took up running and, later, bike riding.

Phipps ran her first marathon at age 51 in 1995 in Lincoln. She did her first Ironman at age 56 and qualified for the Ironman World Championship in Hawaii in her first year of qualifying. She routinely finishes in first or second place for her age group in triathlons and won the World Championship for her age group in Hawaii in 2005.

Kurt Beisch, who works as the race director for Race Omaha, a Nebraska non-profit organization in the multi-sport industry, says the World Championship in Hawaii is like the Super Bowl for triathlons.

Race Omaha puts on several annual racing events, including the Omaha Triathlon, the Omaha Women’s Triathlon, and the Omaha Kids Triathlon. The competitors, Beisch says, are definitely an eclectic bunch.

“They range from newbies, first-time multi-sport athletes, to very decorated nationally ranked athletes,” he says. The women’s triathlon field is made up of about 38 percent first-time athletes, which makes for a great amount of camaraderie.

Indeed, Phipps says, the triathlon competitors make the sport a very social one. This may seem a bit odd for an activity that, on its surface, seems to depend entirely on the individual’s stamina and endurance. But competitors feed off each other’s enthusiasm.

“We have a very good brotherhood of triathletes here in Omaha,” she says. “And I am fortunate enough to know a lot of younger ones and more mature ones.”

Beisch, who is also a decorated triathlete, estimates that about 15 percent of the participants in the field at the events are aged 50 or older, and some of them are some of the most accomplished athletes in the country.

“[They] make me look like a grade-school triathlete compared to the achievements they’ve had in the course of their lifetime,” he says.

Older competitors, he says, have an advantage in qualifying because there are fewer of them, so there’s less competition.

But more so than the competition, Beisch says, triathletes experience a great sense of accomplishment and that “coming across that finish line is an event.

“You have covered a lot of ground, you have pushed yourself in different ways and you have competed in three events,” he says.

Phipps has worked for Nebraska Furniture Mart for the last 39 years, and the company has been very flexible with her hours to allow her maximum training time. When getting ready for a triathlon, her weekly schedule involves two swims, two bike rides, and two runs. She trains 10-20 hours a week for an Ironman and may bike up to six hours a day (though shorter triathlons don’t require as much training time).

She gives the impression of someone who really knows her stuff. In spite of the many jokes she makes about her age, there’s a quickness and vitality to her manner.

She’s also, it seems, just about unstoppable. She has a plate and several screws in each arm and a visible scar running down from her wrist. Before one event she broke her foot and couldn’t take painkillers because painkillers can cause kidney damage. She competed anyway.

This year, she plans on competing in the Boston Marathon for the sixth year in a row. In 2013, she was having a great race and was approximately four blocks from the finish line when the race was stopped and she was escorted to safety.

Later, she saw the local Boston media’s coverage of the bombing from her hotel room. “It was grotesque. Just blood everywhere. Obviously, people crying and moaning. It was just horrible.”

However, there wasn’t any hesitation about returning the next year.

“It wasn’t even a question about going back,” she says. “We weren’t about to let the enemy stop our dreams.”

So what keeps her going? Part of it, Phipps says, is that you compete against yourself.

“You can’t compare yourself to what you were 10 years ago, 20 years ago, 30 years ago,” she says. “Every time you enter a new age group you have to think it’s almost like a whole new ballgame.

“Luckily, they have age groups every five years. You think of yourself as trying to stay as fast as you can in that age group, and it’s the one thing that you look forward to getting older…because let’s face it, getting older is not fun. But, when you do go over that next hump, into the next age group, then you realize it’s a whole new set of personal records for your age. That helps a lot.”