Biles flew in from the left side of the frame, completed a roundoff and a back handspring, and launched into a series of flips and twists. She landed lightly with a deft hop back, her arms up in effortless glee. The move Biles completed is known as a tucked triple double, and it’s one that has been performed in competition by male gymnasts, but never by a female. It does not yet exist in the women’s code of points.

What’s even crazier is that Biles has possibly had this move in her arsenal since 2014. In a tweet from that year, she wrote, “fun fact: the first time I tried a double double layed [sic] out I did a triple double layed [sic] out instead.”

If Biles could (probably) do the triple double in 2014, you might be wondering why she didn’t compete it at the 2016 Olympics. The answer to that question is that most high-level gymnasts don’t unleash their best moves during competition. Every four years, fans and Olympic viewers alike are in awe of the athletic feats displayed by Biles and other gymnasts, but what many don’t know is that they’re not actually seeing all that gymnasts can do. Gymnasts regularly add flips, twists, and connections in the training gym, upgrading skills—or creating brand new ones—that might never make it to prime time.

That means that if you really want to see everything the best gymnasts are capable of doing, you have to go looking for clips of their training sessions. Luckily, Team USA’s current crop of seniors hasn’t been shy about sharing jaw-dropping footage featuring skills that technically don’t exist yet. Biles’s triple double tweet was preceded by one of her throwing her eponymous double layout half out directly into another layout, something former coach Aimee Boorman says she’s also been able to do since 2014 (Boorman also says Biles once did a roundoff double tuck on a beam).

Gymnastics daredevil and 2016 Olympic alternate MyKayla Skinner was once spotted training the triple double, though it looked like she had trouble getting it around. She also once added a full twist to her vault, the Cheng—at the time the most difficult Yurchenko vault in the women’s code of points, and one that she competed with one hand.

Breakout senior and 2019 American Cup champion Leanne Wong recently showed off a quintuple twist (using a trampoline runway and into a pit, but still).

National team member Jordan Chiles started training a front triple twist in 2017, and still plans to one day compete it, she told Inside Gymnastics.

And if we go back a few years, there’s McKayla Maroney’s fabled Yurchenko double back, a vault she admitted to trying in a 2016 interview with the gymnastics podcast Gymcastic, wherein she announced her retirement from the sport.

Maroney expressed some regret in that interview that she never competed the double back, and that’s understandable. A gymnast who a completes a skill that doesn’t yet exist in the code of points (an admittedly shoddy system) during a large-scale competition gets immortalized by having the skill bear his or her name going forward. Biles took advantage of the rule to get her floor skill named for her at worlds in 2013, and her vault at 2018 worlds.

In a sport that expects more and more difficulty from its athletes each year, the policy can lead to something like an arms race. Fans still debate whether Skinner landed the laid out double double before Canadian Olympian Victoria Moors, but Moors competed the skill first, at 2013 Worlds in Antwerp, so it carries her name. The triple-twisting Yurchenko vault, a half-step up from the capstone Amanar, is still up for grabs. Hong Un-jong of North Korea tried to claim the vault at the 2016 Olympics, but under-rotated it and fell. Biles, meanwhile, posted a video of her training it last year, and Skinner’s coach confirmed in an email that Skinner has attempted it as well.

The incentives to push the envelope are tempting. Getting a skill named after you is a way to forever etch your name in gymnastics history, but gymnasts have good reasons for leaving their best skills at home when competition time comes.

For one thing, there’s the risk of injury. Throwing a skill you’re not 100 percent comfortable with just isn’t smart, and there’s a difference between doing a skill in isolation versus doing it in an already jam-packed, adrenaline-fueled routine. Under-rotate a vault like Skinner’s, miscalculate under the bright lights of the competition floor, or run out of energy at the end of a connection-loaded bar routine and you risk a gruesome injury. While warming for the team competition at the 2012 London Olympics, Aly Raisman rehearsed a layout connection similar to Biles’s. She finished awkwardly on the tumbling pass and ended up with no height or control on her connecting layout, landing on her neck. When it comes to skills like the Yurchenko double back, there’s no balking. “Once you’re going for it, you’re going for it,” said Maroney. “When you’re doing a double back, you can’t stop; you’re going to die.”

That doesn’t stop some gymnasts from chucking the hardest skills and hoping for the best. Indian gymnast Dipa Karmakar has competed the Produnova, a vault that scares even the likes of Biles.

Karmakar’s been hit hard in execution for landing in such a heavy squat, but she qualified for the vault final at the 2016 Olympics and finished in fourth. Similarly, Hong Un-jong’s botched attempt at the triple-twisting Yurchenko still left her in sixth place.

Risks can be rewarded, but even in an era where difficulty is favored in scoring, it’s usually wise to avoid getting too crazy and instead focus on doing clean skills in order minimize major execution deductions. In the 2016 vault final, the three competitors who beat Karmakar trailed her in difficulty, but made up for it in execution.

Biles won that final. If you really want to know why she didn’t try for more innovation in Rio, look no further than her medal count: Even with her toughest tricks left at home, she raked in four golds and a bronze. And for Team USA, that’s the priority. “Most gymnasts from top countries don’t prioritize getting a skill named as much as they prioritize hitting routines and winning medals,” says Gymternet Editor-in-Chief Lauren Hopkins. “For these gymnasts who have medals on the line, it’s really only worth debuting a new skill if it’s as consistent and solid as all of the skills they normally perform, but if it looks risky in the gym, most coaches would prefer to keep it in the gym.”

Biles’s legacy will ultimately be her success in competition, for which we can credit Biles and her coaches’ ability to pace her career just right, and to balance risk and reward. And the same goes for her teammates, who brought home four more individual medals in 2016. At last year’s World Championships, the team’s difficulty score was nearly four points higher than the silver medalist, and they did that without deploying a quintuple, a Cheng full, or a triple double.

The next time you see Team USA in action, you likely won’t be seeing all they can do, but all they need to do to win. Maybe one day we’ll see the Biles II on the floor, but until then we’ll just have to keep hoping for more training videos to lose our minds over.