Bill Murray sent out a humorous tweet this week about the 2016 Olympics in Brazil.

It read, “Every Olympic event should include one average person competing for reference.”

Yes, just imagine you or one of your friends competing with Michael Phelps as he powers his way to another gold medal.

Or trying to keep your footing while standing on a 4-inch-wide balance beam, much less doing a head-over-heels 360 degree leap and sticking the landing like gymnast Simone Biles.

Olympic athletes do things far beyond what the average person can do, all while an international spotlight shines on them in competitions decided by tenths of a point or hundredths of a second.

How can these young competitors perform at such a high level in such pressure-packed environments?

Two sports experts interviewed by Healthline said there are a multitude of reasons that these athletes reach this elite level, both from a physical and a mental standpoint.

And the work it takes to get there makes those who watch admire them.

“We are a nation who loves our athletes who pursue their dreams when others put their dreams on the back burner.” said Loren Fogelman, the founder of Expert Sports Performance, and author of “The Winning Point — How to Master the Mindset of Champions. “They represent hope.”

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The physical part

Some athletes are born with a competitive edge.

Dr. Sharon Hame, a sports medicine and orthopedic surgery expert at Ronald Reagan UCLA Medical Center, said genetics can play a big part in an elite athlete’s success.

Some are blessed with great height for sports like basketball and volleyball.

Others have fine-tuned muscles, either fast-twitch or slow-twitch, for sprinting and long distance running.

Others have superb cardiovascular systems, which can help in track, swimming, and other aerobic-heavy events.

For example, there has been talk for years about how Phelps, the holder of almost two dozen Olympic gold medals, is “built like a fish,” with his long arms and large feet and hands.

Or how world champion sprinter Usain Bolt’s 6-foot-5-inch frame and powerful legs allow him to complete 100 meters in 41 strides, compared to about 44 strides for other world-class sprinters.

However, Hame says it’s not all genetics.

Another major component is the years and years of training these athletes put in, developing their muscles, technique, and stamina.

Hame said it goes well beyond author Malcolm Gladwell’s theory that 10,000 hours of practice makes people experts at what they do.

“The amount of training is an important part of this success,” she said.

Hame added that many of these athletes also have a good “training atmosphere.”

They have parents or coaches who support them and nurture them. Good guidance is a key element to being in tip-top shape.

“It’s important for them to have a support system in place,” she said.

But the physical elements, while important, are probably less vital than the mental component when you get to the Olympic level of competition.

After all, if gold medalist Simone Manuel had swum two-thirds of a second slower in Thursday’s 100 meter women’s freestyle final, she would have finished last instead of first.

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The mental factor

Fogelman believes there is initially an “external driver” that propels an athlete into a sport.

It can be that a particular sport is fun, or friends are on a team, or it’s a way to get out the house.

But for elite athletes, Fogelman said, at some point an “internal driver” kicks in.

Those inner motivations run the gamut, but Fogelman said it’s those inward motivations that make these athletes stick with it over the years.

“The more personal the driver, the better,” she said.

Both Hame and Fogelman said almost all elite athletes have an incredible ability to focus, even under intense pressure and worldwide scrutiny.

“The ability to focus is extremely important. It’s what really separates them,” said Fogelman.

This can be when things are quiet, such as on the tennis court or golf course. Or when things are noisy like on the track or the basketball court.

Tenacity is another mental component that Fogelman listed for elite athletes. This not only allows them to train for years, it also pushes them along when they need to make minute tweaks in their technique to gain that two-thirds-of-a-second advantage.

Hame added to her list determination and the goal-oriented ability to accept short-term sacrifices such as skipping a late-night party to achieve long-term success.

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Older athletes who keep it going

At age 31, Phelps is considered old for a world-class swimmer.

This is his fourth Olympics and he’s still winning gold.

Phelps is the most successful of the older athletes at the 2016 Games, but he is not the only one who is past what is generally considered prime for his event.

There’s Allyson Felix, the 30-year-old U.S. track sprinter, Todd Rogers, the 42-year-old American beach volleyball player, and Bernard Lagat, the 41-year-old U.S. distance runner.

You can also add Ryan Giggs, a 42-year-old soccer player, and Jo Pavel, a 42-year-old runner, both from Great Britain, along with Amy Acuff, a 41-year-old U.S. high jumper.

There is also Carl Lewis, who won 10 Olympic medals while competing in four Summer Games between 1984 and 1996. His final gold medal came at the 1996 Olympics, when he was 35 years old.

Fogelman said these older athletes just seem to have a drive beyond reaching the summit. They want to scale the mountain more than once.

“They’re always looking to master that next challenge,” she said.

Fogelman said these veteran athletes make up for any declining physical skills with wisdom gained from experience.

Hame added these athletes also seem to have flexibility, adapting their training and approach to avoid injuries and to hone their skills further.

They seem, she said, to have a different mindset than others, and a deeper desire to succeed.

“I’m not sure the audience watching really understands what an athlete has gone through to get there,” Hame said.