What's happening inside Simone Biles' brain when the 'twisties' set in?

Simone Biles mid-twist during a vault at the Tokyo Olympics. (Image credit: Getty/ MARTIN BUREAU / Contributor)

American gymnast Simone Biles withdrew from several Olympic events this week, including the latest withdrawal from the vault and uneven bars finals, after experiencing a case of "the twisties" — what gymnasts describe as losing control of their body mid-trick and losing sense of where they are in the air. The sensation is not only disorienting, it's dangerous and can lead to serious injury.

"So I was trying a two-and-a-half [twisting vault], and I ended up doing a one-and-a-half. Just got a little bit lost in the air," Biles said in an interview, according to NPR. "I had no idea where I was in the air … I could have hurt myself," she said in another interview, The Washington Post reported. 

Following Biles' decision to forego the team final on Tuesday (July 27), former gymnasts posted to Twitter about their own experiences with the twisties that resulted in broken bones, concussions and dislocated vertebrae; U.S. Olympian Dominique Moceanu, who medaled in gymnastics at age 14, tweeted, "In our sport, we essentially dive into a pool w/ no water. When you lose your ability to find the ground — which appears to be part of @Simone_Biles decision — the consequences can be catastrophic."

Similar to the so-called "yips" in other sports, the twisties represent a moment where, suddenly, an athlete's brain and body lose connection and muscle memory fails, the Post reported. Through their countless hours of training, athletes literally rewire their brains to perform complex movements with a high degree of reliability and precision. So what's happening when a case of the twisties strikes? Live Science asked experts to find out.

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The yips and twisties crop up when athletes suddenly fail to perform the motor skills they've drilled into their brains in practice, but how do they pick up those skills in the first place? Part of the motor-learning process involves learning what physical sensations to expect when executing a new skill, said Kathleen Cullen, a professor of biomedical engineering at the Johns Hopkins University School of Medicine.

"Balance during complex motions, such as gymnastics, requires a real-time comparison between the brain's expectation of sensory input and the actual input," Cullen told Live Science in an email. While in motion, the brain takes in sensory information from the eyes; proprioceptive nerve cells, which relay information about body position to the brain; and the vestibular system, the sensory system in the inner ear that controls the sense of balance. The brain integrates all these signals and compares them to an "internal model" of what the motion should feel like, based on past experiences.

"In order to maintain balance, the brain needs to ask itself a critical question: Did I really want to do that?" Cullen explained.

Simone Biles during women's qualification for the Artistic Gymnastics final at the Olympics at Ariake Gymnastics Center, Tokyo, Japan, on July 25, 2021. (Image credit: Ulrik Pedersen/NurPhoto via Getty Images)

The cerebellum, located at the bottom and back of the brain, plays an important role in generating these internal models of movement; the cerebellum also watches out for any mismatches that occur between the expected sensations of a motion and the actual ones that happen in real-time. If it senses any unexpected motion — say a gymnast's back arcs a bit more than usual during a release from the uneven bars — the cerebellum quickly shoots a message to the spinal cord, which then switches on reflex pathways that help the body adjust itself.

"Our research has shown that the cerebellum actually computes unexpected motion within milliseconds so that we can send an appropriate signal to the spinal cord to rapidly adjust our balance," Cullen said. In addition to switching on certain reflexes when needed, the cerebellum also suppresses reflexes that might otherwise prevent athletes from executing certain skills, Cullen told Scientific American in 2018. For instance, with training, ice skaters can learn to execute super-fast spins with their heads thrown back; the cerebellum quells reflexes that would pull the body back into an upright position, as well as those that control eye motion and could make the skater dizzy.

Through practice, athletes build and refine "very sophisticated" internal models of their movements, meaning they can develop a keen sense of when and how to adjust their bodies to nail a motion each time, whether they're flipping onto a balance beam, executing a flip turn in the pool or pitching a fastball over home plate, she said.

As they develop these internal models of movement, athletes move through various stages of motor learning, Kelli Moran-Miller, the director of sport psychology for Stanford Athletics and a clinical associate professor in the department of psychiatry and behavioral sciences, told Live Science in an email.

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In the early stages of learning a skill, they rely on explicit instructions, visual cues and trial-and-error to learn what to do to execute a given skill.

"When you are first learning a motor skill, error is actually a great teacher," said Gregory Youdan, a scientist who studies human movement and a committee member for the International Association for Dance Medicine and Science. Errors generate feedback from the body's sensory systems, and in the case of athletes, also prompt feedback from their coaches; this process of making errors, receiving feedback and making corrections helps the brain adopt new motor patterns efficiently, Youdan said.

In later stages of learning, athletes can start to focus more on proprioceptive cues and tune into how their bodies feel moving through the skill, Moran-Miller said. With repetitive practice, eventually, "the skill becomes so well-learned that it is nearly automatic and can be performed with very little explicit cognitive input and conscious control over the movements," Moran-Miller said. In other words, with training, athletes no longer need to think their way through the mechanics of every flip, throw or leap.

That said, when under pressure, athletes may try to take more conscious control of their motions, and this process can actually lead to errors, and sometimes the twisties.

"An athlete may try to compensate for increased physiological or cognitive stress or a lack of confidence by trying to consciously control movements that were previously automatic," Moran-Miller said. The resulting motion tends to be "less fluid, less accurate, more strenuous and more error-prone" than it otherwise would be.

"There's a sweet spot, in this arousal level ... where you're able to do the task really well," Youdan said. Some degree of stress can be helpful, as it can boost alertness and focus one's attention, but too much stress can interfere with the brain's ability to initiate learned motor sequences, according to a 2019 report in the journal Frontiers of Psychology.  This may be related to the stress-induced release of glucocorticoid hormones, such as cortisol, since the motor cortex, cerebellum and spinal cord all carry receptors for these hormones. And without that learned motor pattern being initiated automatically, a gymnast can experience the twisties.

Sports psychologists like Moran-Miller help athletes develop strategies to offset the potentially detrimental effects of stress on their performance. These strategies include practicing relaxation techniques like diaphragmatic breathing and using mental imagery to "rehearse" the experience of executing a skill under pressure, she said. Athletes can also develop a routine of rehearsed thoughts and behaviors to help get them into a performance-ready mindset. Coaches and athletes can also try replicating some of the stressful aspects of competition during practices, so that the stakes feel more familiar when it comes time to compete, she added.

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"The closer that the practice environment is to the performance environment, the more transfer of learning that there is," Youdan told Live Science. This environmental context includes not only the physical venue of the sports event, but also sensory inputs like sounds and lights that might be present at the competition, he noted. Of course, replicating these conditions is a particular challenge in the context of the Olympics, during which athletes must quickly adapt to an unfamiliar environment and schedule while also facing a slew of other stressors.

"One thing that is particularly challenging at the Olympic level is that the pressure is not coming just from the performance context itself, but also all the other demands that surround the competition," such as media interviews and the intense competition schedule, Moran-Miller said. When working with athletes, she said she primarily focuses on identifying factors that they can control, so they can stay centered and perform well, "regardless of the circumstances."

But when the twisties do strike, what then? Some gymnasts find they have to retrain the skill that tripped them up, sometimes starting with the basic components and working their way back up to the fully-realized trick, The Los Angeles Times reported. Sports psychologists also work with athletes to determine whether a particular skill itself triggered the twisties, or if specific environmental factors were more to blame.

JaNay Honest, a former University of California, Los Angeles gymnast, told the LA Times that she used mental imagery to overcome a bad case of the twisties, by envisioning herself nailing skills over and over; she then moved on to physical training with foam pits and extra mats. Prior to this retraining, though, she and her coaches began crafting her routines to avoid twists altogether, as that skill kept provoking on the terrifying sensation.

"It's kind of like forgetting how to twist your body in the air," Honest told the LA Times. "It's really scary because when you're doing a skill like Simone does … it's really dangerous."

Originally published on Live Science.

Nicoletta Lanese
Channel Editor, Health

Nicoletta Lanese is the health channel editor at Live Science and was previously a news editor and staff writer at the site. She holds a graduate certificate in science communication from UC Santa Cruz and degrees in neuroscience and dance from the University of Florida. Her work has appeared in The Scientist, Science News, the Mercury News, Mongabay and Stanford Medicine Magazine, among other outlets. Based in NYC, she also remains heavily involved in dance and performs in local choreographers' work.