Anja Niedringhaus / AP

United States' Manteo Mitchell competes in a 4x400-meter relay heat during the athletics in the Olympic Stadium at the 2012 Summer Olympics, in London on Thursday. Manteo had half a lap to go in the first leg of the 4x400-meter relay preliminaries when he broke his leg, and was faced with a choice: keep running or stop and lose the race.

He heard the break. He felt the pain. And he just wanted to lie down.

But after he broke his leg during the semifinal round of the men’s Olympic 4 x 400 meter relay on Thursday, sprinter Manteo Mitchell kept on running, even though, he said, “It felt like somebody literally just snapped my leg in half.”

“It’s impressive both because he’s dealing with pain as well as not having all of his parts in an optimal situation,” says Dr. Balu Natarajan, a sports medicine specialist in Chicago.

He attributes Mitchell’s feat to a combination of the highly trained athlete’s fight-or-flight response to pain and the fact that the bone he broke in his lower left leg, the fibula, absorbs less shock and does less work than the other leg bones.

“Part of it was that the fibula contributes less to weight bearing as opposed to the femur and tibia and part of it is that in that high-energy situation, he has enough adrenaline and endorphins kicking throughout his body that he’s feeling a lot less pain at that moment,” said Natarajan, who also serves on the medical team of the Chicago Marathon.

Had the 25-year-old Mitchell broken his femur or tibia, it would have been nearly impossible for him to finish the race, he said. If a leg bone had to break, he was in a sense lucky it was the fibula.

“If it’s a short enough distance and a high level enough athlete, even with a broken fibula, someone can finish the race,” Natarajan said.

In a statement released through USA Track & Field, Mitchell said the roar of the crowd was so loud that nobody heard his “little war cry,” and he said he didn’t want to let his teammates down. Mitchell finished his heat in 46.1 seconds, only 1.5 seconds longer than the runner of the next leg; the U.S. qualified for the finals and finished in the fastest time ever run in the first round of the relay at the Olympics. On Friday, the U.S. team went on to win a silver medal, thanks in part to Mitchell's sacrifice.

In a high-stakes event like the Olympics after years of training, athletes sometimes will stop at nothing, experts say.

“There’s so much that’s tied into the psyche during a race like this, it really can override a lot of things we would feel outside of such a high energy situation,” Natarajan said. “If the same thing happened on training run and no one was around, he would very likely have stopped.”

“Anybody who has trained for a particular event for four years, really they have one goal, and between that and the tremendous conditioning and excellent biomechanics, it’s really the perfect confluence of factors that might allow someone to overcome a break like this,” he said.

Mitchell said he had slipped on the stairs a few days earlier, but had it checked out, felt fine and didn't think much of it. Mitchell’s strong finish in the race was a clear example of a top athlete’s ability to put mind over matter, says Frank Smoll, a professor of sport psychology at the University of Washington.

“It’s a very good illustration of how highly motivated they are and their willingness to pursue and persist and play through pain, so that the importance of what they’re doing really outweighs the potential negative consequences, in this case, physical harm,” he said.

“They’re highly dedicated athletes, they’re courageous, and they’re willing to, at their own self-sacrifice, give it their all,” Smoll said.

The training Olympic athletes receive in "attention control," the ability to block out distractions like pain, helps them succeed, Smoll said, adding: “It’s not just the physical ability that makes the elite athletes but the mental preparation is what makes them excel.”

The U.S. men's 4 x 400 relay team won a silver medal on Friday; Mitchell, who has been fitted with a boot and crutches, will receive a medal with the rest of the team.

Related: 

• What is with that weird tape Olympians are wearing?
• Give McKayla Maroney a break: 2nd place is tougher than 3rd 
• You've just won a gold medal! So why are you trying to eat it?
• Gold medal mom: I felt selfish training for Olympics
• Video: Decathletes are amazing

Emmanuel Dunand / AFP - Getty Images

Mmm, gold medal ... om nom nom. Team USA chomp on their medals after winning the women's team gymnastics final on July 31. From left to right, we have Mckayla Maroney, Kyla Ross, Alexandra Raisman, Gabrielle Douglas and Jordyn Wieber.

After medal-winning Olympians stand on the platform, receive their medals, and solemnly listen to the gold medal winner’s national anthem, they leave the stage and face an army of photographers. In front of the flashing lights, many winners grab their medals and take a bite.

It takes years of grueling training and competition to nab gold at the Olympics. So why do the winners immediately chomp on their hard-earned prizes?

The simple answer: Because the photographers ask them to, says David Wallechinsky, president of the International Society of Olympic Historians and author of “The Complete Book of the Olympics, via email.

Related photos: Olympians biting their medals

While Olympic historians aren’t sure which athlete started the trend, they believe the athletes nibble their prizes to test the metal. People once bit gold coins try to make an indent; a small tooth mark in a coin assured it consisted of real gold, which is more malleable than counterfeit gold-plated lead coins. 

“We know that only in 1912 the gold medals were real gold and that in all later Olympics the gold medals were made from silver with a gilt layer to show it as being gold,” explains Tony Bijkerk, secretary-general of the International Society of Olympic Historians via email. The 2012 medals contain 1.34 percent of gold, making it one of the biggest medals.

Um, how do we break this to you, Team USA? You didn't actually win gold

“Unfortunately, the gold layer sometimes had a tendency to fade over the years. Fanny Blankers-Koen, the heroine of the 1948 Olympics in London, who was a good friend of mine, once told me that she had to have her four gold medals re-gilded two times over the years.” (Blankers-Koen was a 30-year-old mother of two who medaled in running events, helping to prove women could be as athletic as men.)

Even though the medal isn’t solid gold, Bijkerk suspects that Olympians could make a mark in the medal, depending on how hard they bite. And some really sink their teeth into their prizes. At the 2010 Winter Olympics, German luger, David Moeller, who won a silver medal, broke his tooth while mugging for cameras and showing off his bite.

Psychologist Frank Farley believes that medalists bite their medals because, at this point, it’s what winning Olympians do.

“Sports all have their eccentricities,” says Farley, a professor from Temple University in Philadelphia and former president of the American Psychological Association. “If you want to be part of the winning zeitgeist, that winning culture, you participate in that winning practice.”

But he believes that medal biting is more than Olympians simply acting like winners. “It makes your medals yours,” Farley says. “It’s an emotional connection with your accomplishment.”

And even if the Olympians do indent their medals, it makes the prize individual; bite imprints are as unique as the swirls on our digits.

“The concept of the icon, something representing something else, is pretty deep in all of us. In the Olympics, they have a twist on it; it’s like imprinting [yourself] there for all of time.”

Anthony Quintano / NBC News

Ah, the sweet taste of victory! U.S. swimmer Ricky Berens takes a bite of his gold and silver medals on the TODAY set in London.

Related:

• What is with that weird tape Olympians are wearing?
• Give McKayla Maroney a break: Settling for 2nd can be tough
• Chinese weightlifter's hairy mole: Everything you never wanted to know

Want more weird health news? Find The Body Odd on Facebook.

AP Photo/Mike Groll

Zhang Jie of China reacts while competing during the men's 62-kg weightlifting competition at the 2012 Summer Olympics, Monday, July 30, 2012, in London.

What's the most shocking sight in the Olympics so far?  It’s not Michael Phelps failing to medal in the 400 IM.  Nor is it Jordyn Weiber getting eliminated from the gymnastics all-around finals. 

The most shocking sight to me is Chinese weightlifter Zhang Jie’s big, hairy facial mole.

Zhang sports a mole on the side of his chin that must measure at least half an inch in diameter.  Long, wiry, black hair protrudes from it, resembling the whiskers of a cat. 

As a plastic surgeon, I recommend that he have the mole removed.  It resembles a congenital hairy nevus, which carries a 0.8-4.9 percent risk of turning into skin cancer. The best treatment for moles like this is surgical excision. 

So why hasn’t Zhang had it cut off? 

Even more important, why doesn’t he clip those hairs?

According to the Chinese Fortune Calendar, dark moles are often considered good luck. Hairy moles signify even better luck than bald ones, as they are regarded as healthier. This belief may actually be supported medically: Cancerous moles often lose their hair, as the cancer cells invade the hair follicle, causing the hair shafts to fall out.  Therefore, hairy moles are considered less likely to be cancerous than non-hairy ones.

So was Zhang’s congenital hairy nevus good luck? 

Not really. Although he was the favorite to win the 62-kilogram competition, Zhang ended up placing fourth. 

Time to call the plastic surgeon.   

Dr. Anthony Youn is a Michigan-based cosmetic surgeon and frequent NBCNews.com and TODAY.com contributor. He is the author of the book "In Stitches," a humorous memoir about becoming a doctor. 

Want more weird health news? Find The Body Odd on Facebook.

By Chris Gorski, Inside Science

Call them pre-performance tweaks, athlete hacks, or just plain smart. In an effort to extrude every last bit of performance from their bodies, Olympians are likely to ingest some strange-sounding supplements in their final preparations for competition.

Beetroot juice, bicarbonate of soda, and caffeine may sound like the ingredients for a particularly colorful science-fair project, but sports physiology experts say these competition-legal supplements may significantly improve an athlete's performance.

"A one-percent difference in performance is something that will separate the guy who wins the 100 meter gold medal from the guy who comes last in the race," said Michael Gleeson, an exercise biochemist at Loughborough University in Leicestershire, U.K.

Caffeine is one supplement that many non-athletes rely on every day. Although athletes' use was once subject to limits under antidoping rules, it is no longer a regulated substance. The athletes are seeking many of the same benefits that the rest of us gain from a cup of coffee.

Beyond the benefits that most people recognize, such as increased alertness, "[Caffeine] also improves a lot of other physiological parameters, so a lot of people take it," said Keith Baar, an exercise physiologist at the University of California, Davis.

"There's no real reason why athletes wouldn't be taking caffeine," said Gleeson. "The dose that's needed to improve performance through a central brain stimulant effect is fairly low."

One limit to performance in many events that last longer than a minute, but usually less than 10, is the build-up of lactic acid in muscles. When intense exercise requires more energy than the body can provide through the aerobic process that uses oxygen, it creates energy using a different process, which ends with the formation of lactic acid. Buildup of this acid causes a burning sensation and can impair muscle contraction, slowing down athletes.

Some Olympians will take bicarbonate -- better known as baking soda -- to counteract this process. In theory, having a supply of bicarbonate in the blood allows it to buffer the acid's hydrogen ions, slowing down any buildup in the muscles, and helping to improve performance.  

Bicarbonate is used by those athletes that can abide its often significant effects on the digestive system. Once it reaches the stomach, bicarbonate produces carbon dioxide, which can cause flatulence, bloating and other unpleasant, potentially performance-impairing side effects.

"If an athlete can actually physically tolerate taking that supplement without too much gastrointestinal problems then it may well improve their performance," said Gleeson.

But recent scientific studies suggest that it might not actually work as well as was indicated in early studies, said Baar.

Juicing a beet provides a deeply colored liquid rich in chemicals called nitrates, and promises to provide multiple sources of assistance to athletes, both physiological and psychological. Nitrates are also found in other vegetables such as Swiss chard and roots.

Studies have shown that beetroot juice alone can improve performance by 2-3 percent in events lasting 20-30 minutes, said Baar.

"[F]or events lasting more than a minute and lasting up to several hours, it's a potentially performance- enhancing supplement," said Gleeson. "It essentially will improve endurance exercise performance by making you more efficient in the use of oxygen."

"Efficiency is one of the key things that's going to distinguish between a winner and just somebody who's there to compete," said Baar.

Beetroot juice also has an additional, instantly recognizable effect that could have a significant psychological impact. The vegetable's natural color can add unfamiliar hues to athletes' waste products.

"You're going to pee purple, you're going to poo purple," said Baar. "There's nothing quite as good for a placebo as seeing, 'Oh yeah, I'm taking the beetroot, there it is, everything is working really well.'"

In some cases, a supplement's physiological effect of might not be the most critical part of its contribution to an athlete's performance. Believing that something improves performance, whether it is a preparation ritual, or a supplement, might offer its own performance-enhancing effect.

This is one reason why it's so difficult to analyze the true effects of many supplements. A 2-3 percent difference would likely be easily recognized in a scientific experiment, but a lesser improvement might not, Gleeson indicated. Olympic medals are often decided by substantially smaller margins.

Athletes take many other supplements, both in training and in competition. But a winning performance does not prove that an intervention works.

"One of the many problems in this field, this whole area, is that to scientifically prove that something improves performance is very difficult to do for anything that might only have a relatively small effect," said Gleeson.

This story originally appeared on InsideScience.org.

Related:

• Psst: Asparagus pee. Are you in the club?
• Pee shivers: You know you're curious

Want more weird health news? Find The Body Odd on Facebook.

Timothy Clary / AFP/ Getty Images

U.S. swimmer Garrett Weber-Gale (L), shown with Michael Phelps, demonstrates the universal and time honored signal for victory at the Beijing Olympic Games on August 11, 2008.

Flat screens, phones and laptops soon will blaze with a body-language blitz: sweaty palms clasping mouths in disbelief, muscled arms folded in disagreement and – the sweetest Olympic pose – two fists hoisted aloft in displays of golden bliss.

“That position – the arms raised high – evokes triumph and it’s very ancient,” says Margaret J. King, director of the Center for Cultural Studies & Analysis in Philadelphia.

That traditional victory stance, rooted in the older, limbic portion of our brains where base emotions are fueled, may have been flashed when the earliest humans celebrated their first conquests, King suggests. Simply put, it pretty much predates Rocky,  "The Breakfast Club" and Notre Dame's "Touchdown Jesus." 

“I’m a cultural analyst but I use anthropology and I would bet that comes from a good hunt, from having successfully hunted and killed prey,” King said. “The Plains Indians’ dances used this as well, where the arms were over the heads, and that’s really, really important for group morale: ‘We won!’ ”

Scholars speculate that Neanderthals some 30,000 years ago had neck structures that gave them the ability to produce sounds similar to modern humans. If that’s so, why is body language still such a rich and vital part of our communication? Why didn’t evolution long ago wean away our need to silently reveal our inner feelings through postures and gestures?

“We still use body language because that’s the way our brains worked (eons) years ago when we first became human,” King said. “That brain is still ticking away; all research based on evolutionary psychology demonstrates that we are living in the 21st century with that same ancestral brain. This is what is called hard wiring. We still have the same bodily workshop. We just do different stuff in that workshop.”

“Body language is not an either-or situation,” adds Dennis Kravetz, a Scottsdale-Ariz.-based psychologist who specializes in male-female communication and body language. “If speech is more sophisticated than body language, then why haven’t chimps, dogs, and other animals developed speech as part of their evolutionary history? Rather, body language enhances communication.”

Evolution may have stripped away many outmoded human parts and proclivities that we no longer need but body language remains an essential tool in our modern communication kit, both Kravetz and King contend.

“We send out signals because that's the way it has worked for millennia: anything human beings have been doing for that long is not likely to change anytime soon,” King said. “It’s the language of sociability: You can tell if someone likes you. Can we work together? Can I trust you?

“We’re looking at body signals all the time to tell, first of all, if people are safe or unsafe. That’s one of the first things we look for in business is trust - is this a safe person to deal with?”

Likewise, if someone is marrying into a family, that person’s initial body language is carefully scanned by the family, she added, as they “look for the signals that say this is a consistent person, or that his words and language are not matching his body language, meaning he is not a person you can trust.”

Fair enough, but according to Charles Darwin’s theory of natural selection, certain traits are passed from generation to generation that allow human offspring to be better suited to survive this world. How does unintentionally broadcasting your anger, sadness or frustration through “negative body language” help you – or your great-great grandchildren – endure? Why hasn’t evolution sapped those awkward poses (hands on hips, crossed arms) from our nonverbal playbook?

While those signals subliminally convey bad feelings, they also alert others around us – hopefully friends or colleagues – that the person fidgeting, fumbling or looking forlorn may be in some emotional trouble. These unintended expressions are, in a sense, silent 911 calls.

“Communicating anxiety or sadness is not bad at all,” said Kravetz, author of "Relating Effectively.” "These are just as important … as feeling happy, excited and other positive states of mind. Body language helps us more fully communicate with another humans irrespective of what we are (saying).”

And in the workplace, if such “negative” body language is expressed among close company allies, “the sense of the group is: this guy is frustrated; something is off base here,” King said. “It’s a signal that the group needs to address this issue together – that we need to do something

“We have to work in teams. Human life is highly social and highly territorial. It explains a lot of our behavior,” she added. But like our ancient ancestors, "body language helps us relate to other people.”

Related stories:

Sneak a peek at Team USA's official Olympic outfits

Want more weird health news? Find The Body Odd on Facebook.

Related: 

No sex necessary: Women have orgasms at the gym

Heart attack? Nope, just a spin class

When marathon runners leave a toenail behind

Want more weird health news? Find The Body Odd on Facebook.