Rio de Janeiro, Brazil (CNA/EWTN News) - Biles, a record-shattering gymnast with a sparkling smile and bubbly energy that shines through her routines, is the U.S. gymnastics team fan favorite and the gymnast to beat for any chance at the gold.
"Biles competes with a joy and abandon that has been lacking in women's gymnastics in recent years," wrote Liz Clarke for the Washington Post. "All too often, grim-faced pony-tailed youngsters clench their jaws, furrow their brows and inhale an ocean's worth of air before hurtling into rigorous tumbling passes. Their feats may be acrobatically eye-popping, but the strain of pulling them off is palpable."
"Biles, by contrast, exudes utter delight, competing as if the four-inch-wide balance beam is the sidewalk in front of her house, the vault and uneven bars mere elements of her backyard swing-set and the mat a magic carpet for high-flying fun," Clarke wrote.
The Texas teenager is a four-time national champion and the first female gymnast in history to win three consecutive world championships. The complex moves written into her Rio routines - including her signature series of flips now called "The Biles" - give her an edge before she even performs.
But behind her jaw-dropping performances is a strong family and faith life that Biles (literally) carries with her.
In a recent interview with Us Magazine, the athlete unpacked her Olympic bag, explaining the significance of each item. Along with her bottled water, bobby pins, Beats headphones and cheetah-print umbrella, Biles carries a white rosary.
"My mom, Nellie, got me a rosary at church," she told the magazine. "I don't use it to pray before a competition. I'll just pray normally to myself, but it's there just in case."
Biles was adopted by her grandparents, Ron and Nellie Biles, when she was five years old. Her mother, a drug addict, had struggled to care for Simone and her siblings.
After the adoption, Simone has called Nellie and Ron "mom and dad." She attends Sunday Mass with her parents, and regularly lights a candle to St. Sebastian, the patron saint of athletes, before big events, according to olympic.org.
Katie Ledecky is also one of the top athletes to watch at this year's games.
A 19 year-old swimmer, two-time Olympic gold medalist and nine-time world champion, Ledecky returns to the Olympics after taking home the gold in the women's 800-meter freestyle swim at the summer games in London in 2012. At the time, she was just 15 years old.
The Bethesda, Maryland athlete has no obvious physiological advantages. Measuring in at 6 feet tall, she is often on the shorter end of the swim roster. Her hands and feet aren't particularly large, and her general physique offers her no upper hand - so much so that a summary of her physical-assessment tests at the U.S. Olympic Training Center referred to her as "remarkably unremarkable."
But what is remarkable about Ledecky is her inner drive. A young woman with a gentle demeanor outside of the pool, Ledecky swims with an "aggression and the kind of fury" the moment she begins a competition. She's adopted a type of "galloping" stroke typically used by male swimmers like Michael Phelps, and has a "tough as nails" determination to be the best, according to her coaches.
"She's the greatest athlete in the world today by far," Michael J. Joyner, an anesthesiologist and researcher for the Mayo Clinic in Rochester, Minn., specializing in human performance and physiology, told the Washington Post. "She's dominating by the widest margin in international sport, winning by 1 or 2 percent. If [a runner] won the 10,000 meters by that wide a margin, they'd win by 100 meters. One or 2 percent in the Tour de France, over about 80 hours of racing, would be 30 or 40 minutes. It's just absolutely remarkable."
Like Biles, Ledecky has shattered world records. She is the current world-record holder in the 400-, 800-, and 1,500-meter freestyle (long course). She also holds the fastest times in the 500-, 1000-, and 1,650-yard freestyle events.
Also like Biles, Ledecky's Catholic faith is central to her identity.
Ledecky attended Catholic school - Little Flower School in Bethesda through 8th grade, and then Stone Ridge School of the Sacred Heart for high school - her whole life.
"My Catholic faith is very important to me. It always has been and it always will be. It is part of who I am and I feel comfortable practicing my faith. It helps me put things in perspective," Ledecky told the Catholic Standard in a recent interview.
She also confirmed that she says a "Hail Mary" before each event.
"I do say a prayer - or two - before any race. The Hail Mary is a beautiful prayer and I find that it calms me," she told the Catholic Standard.
After winning her first Olympic gold 4 years ago, Ledecky paid a visit to the convent of the sisters from her grade school, Crux reported. She wanted to thank the sisters for their support over the years, and give them a chance to celebrate with her.
Catherine Ronan Karrels, Stone Ridge's head of school, told Crux that Ledecky "is so grounded in her faith, and supported by a really loving family and community. She's an amazing young woman, who happens to swim."
Catch Biles and Ledecky this week and next on NBC as they compete in the 2016 Olympics in Rio.