If two people repeatedly slap each other alongside the head, it might seem obvious that they are putting themselves at risk of serious injury. In a recent study, researchers quantified just how dangerous this is, confirming ongoing warnings from the medical community about risks of slap fighting. 

Competitive slap fights were once primarily underground battles of savagery, with YouTube videos of matches in Eastern Europe emerging around 2017. Video compilations featuring “Vasily the Dumpling,” also known as Vasil Kamotskii, a pig farmer from Siberia, went viral. Seeing the potential draw, Ultimate Fighting Championship founder Dana White got behind slap fighting, and TBS ran a one-season reality show in 2023 that aired matches in White’s Power Slap league, after the Nevada Athletic Commission approved the sport. Slap fighting is also now legal in Texas, Florida and California.

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In the Power Slap league, fighters take turns slapping one another while standing in designated boxes across a special table. The bouts last two to three rounds, with judges issuing scores based a 10-point scale after each round. If a defender is knocked down and does not rise by the count of 10, the striker wins. 

The rules require fighters to wear mouth guards and cotton, inner-ear protectors, but they may not wear headgear. Strikers must deliver flat, open-handed slaps while defenders hold their hands behind their backs with the aid of a stick or towel. Strikers can hit the side of the defenders’ faces between the chin and eye-line, avoiding the mouth, eyes, ears and temple. Defenders cannot duck or even flinch. If they do so more than three times in a round, they are disqualified. 

Judges, referees and doctors are all on hand – even “catchers” to grab defenders if they look like they’re going to hit their head or fall off the stage.

The sport has faced criticism. Slap fighting has the “effect of delegitimizing the UFC and validating old criticism, wrongheaded as it might have been, that the organizers were always just building a business based on bloodlust,” Jon Wertheim wrote in Sports Illustrated in 2023. His colleague, Mathew Riddle, wrote that “White’s ‘Power Slap League’ shows a concerning disregard for the evolution of the sport, and takes a deep plunge into the ‘human cockfighting’ narrative that the UFC tried so hard to avoid.” 

White has maintained that slap fighting is the next main attraction in combat sports and has claimed it is safer than boxing or mixed martial arts, because there is no sparring and because defenders usually take about three head blows per bout, as opposed to 400 or more during boxing. 

The medical community, however, has expressed strong concerns about the dangers of head injury and brain trauma for slap fighters. Last week, researchers from the University of Pittsburgh School of Medicine published a warning letter in JAMA Surgery, saying they found nearly 80% of the 56 fighters involved in their study had at least one “visible sign of concussion” in 78 fights examined on videos. They called their research the first academic study about the sport. 

“Slap fighting may be entertaining to watch as a lay viewer, but as medical professionals, we found some aspects of the competitions to be quite concerning,” study author Raj Swaroop Lavadi, said in a news release. “Our end goal is to make all professional sports safer for the neurologic health of the athletes. It is really difficult to ban any sport, but it is possible to raise awareness about the associated harms.”

In 2021, Polish slap fighter Artur Walczak died after suffering head trauma during a slap fight match. Retired slap fighter Kortney Olson told the BBC that her eyes rolled back once from a strike in a slap fight. “After I regained consciousness, I stood back up to get to the table and reset, but lost consciousness again and wound up doing a forward roll,” she said. “I don’t have any recollection of doing a forward roll.”

For the Pitt study, researchers analyzed 333 slaps from videos, recording signs of concussion from “diminished awareness of the environment” to loss of consciousness. In more than half of the slap sequences, participants showed signs of concussion. Competitors exhibited “motor incoordination,” “blank and vacant” expressions and were “slow to get up” in nearly 40% of the analyzed sequences.

“Clinically, concussion can show up in different ways, but each can result in short or long-term disability and socioeconomic distress,” study author Dr. Nitin Agarwal said in a release. “As a physician who has a background in martial arts and is passionate about combat sports, I remain concerned regarding the frequency of overt signs of concussion among slap fighters.”

The Power Slap league streams bouts free to worldwide audiences through Rumble. 

Last year, White fell under scrutiny after he was caught on video slapping his wife after she allegedly slapped him first. The Associated Press reported at the time that White said he would “not self-impose” a punishment.

“What should the repercussions be?” White asked rhetorically in an AP interview. “I take 30 days off? How does that hurt me? … Me leaving hurts the company, hurts my employees, hurts the fighters. It doesn’t hurt me.”

The Pitt researchers said they will continue to assess the dangers of slap fighting to “help inform participants, officials and ring-side physicians, while also providing a starting point for improved safety regulations going forward.”