On Sunday, Ivonne Mosquera-Schmidt swam 450 meters, biked 10 miles, and ran five kilometers in the Upper Main Line YMCA's triathlon.

All without seeing a thing.

Yet the completely blind, pint-size Center City woman is so sure-footed, so fast, that after one recent race a referee checked her blackout glasses — which all vision-impaired runners must wear to level the playing field — to make sure she wasn't cheating.

"For me, it's not a big deal," she said about competing against world-class athletes without even a sliver of light or shadow to guide her.

Instead, she uses a human guide and, as she demonstrated during a training session at the Y four days before the race, her fingers.

She arrived holding hands and walking at a brisk clip with her husband, John Schmidt, whose sturdy, drill-sergeant frame makes the 4-foot, 11½-inch, 88-pound Mosquera-Schmidt seem even tinier. Schmidt took a map of the running course and guided his wife's lithe, childlike fingers over the sheet of paper.

"The longest stretch is just short of half a mile — then there's a little bridge," her husband said.

"Is it wooden?" Mosquera-Schmidt, 34, asked.

"No. Paved." Added Schmidt: "You won't even feel it."

Moments later, the couple stripped down to running clothes and began racing toward the first hillcrest of the course. Mosquera-Schmidt — one of the world's top blind triathletes — ran side by side with her husband, tethered to him by a short cord wrapped around her waist.

Twenty-four minutes later they raced back into view, five kilometers (3.1 miles) closer to Mosquera-Schmidt's goal of winning her division in this fall's World Paratriathlon in New Zealand, and eventually competing in what is slated to be the first Paratriathlon in the Summer Paralympics in Brazil in 2016, when she will be 39.

That hardly seems an impossible mission for a woman who has climbed Mount Kilimanjaro, danced ballet at Lincoln Center, finished 13 marathons, and earned a degree in mathematics from Stanford University and an M.B.A., all since losing both eyes to retinal cancer at age 2.

A yoga aficionado, master in the Japanese art of Reiki, and a vegetarian, Mosquera-Schmidt moves with an aura of spirituality. "The type of energy you put out is what the universe gives back," she says. But the universe has also given her the soul of a fierce competitor.

Five years ago, she pushed to excel in the triathlon after friends scoffed at the notion she could compete in the swimming portion using the backstroke. She said she told them, "The hell with you," defeated everyone in her class, and now says the episode delivered a message to any naysayers:

"Don't doubt me."

Mosquera-Schmidt's infancy was shrouded in doubt. Born in Colombia and diagnosed with retinoblastoma, or retinal cancer, she and her mother traveled to New York for medical treatment that included removing both eyes to prevent the cancer from spreading. "I don't remember any of it," she says.

Her father and two older sisters eventually joined them in the United States. It was a sacrifice; Mosquera-Schmidt's mother had been a teacher in Colombia but found work in New York as a teacher's assistant, while her father — chief financial officer of a bank — became a school guidance counselor.

But her parents also instilled the notion there was nothing she couldn't attempt. "My parents raised me pretty much as a sighted child. When my sisters had to do chores, I did chores," she said. "My mother thought, 'If I'm not around, you'll have to do it.'?" And so the sightless child climbed trees and roller-skated with the sighted kids.

When Mosquera-Schmidt was 9, she joined a ballet program for blind students that was launched by the renowned Jacques d'Amboise and the National Dance Institute. The troupe performed at venues such as Lincoln Center and the Kennedy Center; Mosquera-Schmidt said she was the only girl in the program who was completely blind, unable to see even lights or shadows.

The young ballerina did pirouettes and leaps and once danced across the stage by herself in a circle. "Once you get on stage, it's really about measuring steps," she recalled in a matter-of-fact nature. "You commit all that to memory like clockwork. It's very mathematical."

Her former teacher is more effusive. "She always had a bright, glowing expression of joy on her face," d'Amboise said by telephone. "She relished moving and did not want impediments to stop her."

D'Amboise recalled the time Mosquera-Schmidt ran fearlessly up a narrow flights of stairs with the other dancers.

The math skills that served Mosquera-Schmidt so well on the dance stage propelled her to her degree at Stanford, and later to an M.B.A. degree at Baruch College. She eventually landed a job with Dow Chemical, which led her to Michigan and then a couple of years ago to Philadelphia, where she works as a project manager in information systems. She frequently walks the mile and a half to work from her home at Broad and Fitzwater — arguably her least strenuous physical activity.

Over the years, Mosquera-Schmidt has tackled an increasingly more difficult roster of sports that includes skiing and long-distance running, which became her passion after college until she eventually competed in the Boston Marathon in 2007. She loves the open nature of marathons. "You run where the elites run," she said. "You can't play basketball with the elites, or skate with the Flyers."

It was on a cross-country ski trip in Colorado for people with disabilities that she met her future husband in 2005. Schmidt — a former dairy farmer — was there as a guide for another skier, although Mosquera-Schmidt recalled that "he did follow me around all week."

When Mosquera-Schmidt took the job with Dow at its headquarters in Midland, Mich., she decided to call Schmidt even though he lived a couple of states away, on a farm in Minnesota. She left a message on his machine: "I've moved out and I don't know anyone, and you don't have to call back if you think this is weird." He called back two hours later, and they've been together ever since.

Their partnership is also a good thing for Mosquera-Schmidt's athletic ambitions, since competing as a blind triathlete requires considerable coordination and planning. In a meet, she will race with a female partner whom she is tethered to in the running and swimming events and who guides on a tandem bicycle.

"They're not allowed to provide power and they can't pull you or you will get disqualified," she explained. In just a few short years, Mosquera-Schmidt has been at the forefront as triathlons for the blind have gained a higher profile.

USA Triathlon said the first paratriathlons were held in the late 1980s and estimates there are 150 active paratriathletes in the United States — a number that is expanding. There's no exact figure on the number of blind competitors, although that class saw a combined 13 finishers in the last three national championships.

In 2009, Mosquera-Schmidt finished the World Paratriathlon in Australia and was declared champion in her class because, as she put it, "there was just one. Me." The next year in Hungary there were three blind triathletes at the world meet — and she won a silver medal.

Now, Mosquera-Schmidt is driven by a desire to compete in Brazil in 2016. She calls the Paralympics "one of my dreams," and does not believe her advancing years will hinder her. "With triathletes," she said, "age can be to your advantage."

Logistics can be more complicated. During their recent visit to the Chester County YMCA, Mosquera-Schmidt and her ever-attentive husband spent considerable time going over the complicated transitions from pool to bike to the running course.

"Four steps up," he told her as they went to the pool. He was constantly talking, informing. "There's some corrugated stuff" — on the ground — "and six lanes and a narrow ledge, there's a short, four-foot rail on the left and a ladder into the pool."

It's a lot to remember, but there is no doubt that Mosquera-Schmidt will master it just like all the many other things she's done.

Afterward, Schmidt said his wife had inspired him to strive and taught him that "there is no limitation and there shouldn't be. Our only limitations are the ones we put on ourselves."

Sunday's race was a sprint, about half an Olympic-distance triathlon, which she has also done. The only blind athlete, she finished 132d out of 269 competitors and seventh out of 16 in her age group. Her time: 1 hour, 22 minutes, and 17 seconds.

"She is absolutely fearless," said her guide, Rebecca Smith of West Chester. "She has an uncanny ability to take the information you give her — the cues or the feedback on her strokes — and implement it."

And on this particular run, she was so fast, so sure, as usual, of where she was going that it felt to Smith as if she were the one following along.

"I said, 'Are you sure you can't see?'?" Smith said. "She's so fit and strong. She just bounces up those hills."

Contact Kathy Boccella at 610-313-8123 or kboccella@phillynews.com.