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Mack Kuhr

16 Behind-the-Scenes Secrets of Stunt Performers

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Mack Kuhr

Whether it’s a kung fu fight, car chase, or stair fall, most film fans can name a favorite action sequence that wouldn’t have been possible without a stuntperson. These men and women, who arguably have one of the most dangerous jobs in Hollywood, have come a long way since the days when Buster Keaton and other silent film-era performers did all their own stunts. We talked to several film and television stunt performers for some insights into their risky—if highly entertaining—trade.


A stuntman rappels from a Jeep lifted by a helicopter during a promotion for Universal Studios. Image credit: Getty Images

It seems like only a special type of person would be drawn to the sometimes dangerous world of stunts: someone who is fearless, thrives on adrenaline, and spent their childhood climbing to the highest tree branches. And indeed, many stuntpeople were early risk-takers. “I have studied karate since I was 7 or 8 years old,” says Grant Koo, a stuntman and stunt driver known for his work in Transformers: Age of Extinction (2014) and on the television show The Blacklist. “I used to watch all of those cheesy kung fu movies on a Saturday—and beat the living crap out of my couch!”

But not all stunt performers start early. “My parents never let my brother and I participate in sports when we were younger. They were afraid we’d break an arm,” says Vera Lam, a stuntwoman based in New York. “I’m certain I failed my fitness test in grade school except for the flexibility portion.”


Some stunt performers parlay a background in martial arts or another athletic pursuit into a career, while others begin as actors and move into stunts. Jennifer Lamb, a stuntwoman and stunt coordinator who has worked on 10 Coen brothers movies and other high-profile projects, transitioned into stunts from the world of soap operas. Lamb was playing a waitress on One Life to Live when she met stunt coordinator Danny Aiello III, who believed that her toughness, ability to take direction, and small size would serve her well in stunts. He also gave her her first break—getting tossed off the balcony of a beach house in the Hamptons.


Grant Koo in a death scene for the TV series The Originals. Image credit: Grant Koo.

In the course of their work, stuntmen and women come as close to experiencing catastrophic events as one can without actually, well, going through them. Lamb says, “I have hung by my ankle under a hot air balloon, leapt out of a burning building 60 feet up, gotten dragged behind cars, crashed through a barn in a Ford Model T—none of which seemed crazy to me.”

Koo might have the most impressive all-in-one experience, though. In Transformers: Age of Extinction, he performed in a scene where he and his fellow stuntmen ran from 500,000 gallons of water being emptied from five 100,000-gallon tanks, while at same time dodging boats, buses, and cars being dropped from the sky. “That was one of the craziest days I’ve ever had,” he says, “but very rewarding.”


Mack Kuhr in stunt rehearsals with action cinematographer Richard Clabaugh for the film Abysm (2016). Image credit: Mack Kuhr

Koo describes himself as a “utility player,” or a well-rounded performer skilled in all aspects of stunts. But even within that, there are certain areas he has gravitated toward. “I like to do the fights, the falls, and the driving,” he says, calling himself a “crazy driver” even in real life. 

Mack Kuhr, a stunt performer and Keanu Reeves's body double in both John Wick (2014) and John Wick: Chapter Two (2017), has built early experience with military-grade firearms into a specialty. His father was in the military, and his studies in strength and conditioning at Virginia Tech led to training with Navy SEALs at Virginia Beach. Kuhr got his stunt break on The Dark Knight Rises (2012), when director Christopher Nolan was in need of someone who could handle a “hot” HK G36 submachine gun (one that contained blank bullets). Meanwhile, Jared Kirby, a fight director and stage combat instructor in New York, has spent years perfecting a different sort of weapon—he specializes in historic and classical fencing. 


Jared Kirby (center) working fight choreography for Kevin Keating: Vampire Hunter. Photo courtesy of

Stuntpeople sometimes show up on set without knowing exactly what stunt they are going to be asked to perform. As Koo explains, occasionally they “know when it is and where it is, but not what it’s going to be.” As a consequence, they have to be prepared to deal with new experiences. Lamb says she had never even been inside a helicopter before she was asked to cling to the outside of one while working on the Neil Jordan film In Dreams (1999). Kirby says he likes to throw curveballs at his students during fight training—such as littering a stage with garbage or turning out the lights—so that they won’t freeze up when conditions change on set. On the other hand, every stuntperson has his or her limitations and stunts they won’t do, like fire burns and high falls, which are specialties in themselves. Koo, for instance, says he won’t do fire scenes, to protect his face.


A good film crew takes every precaution to keep their members safe, and injuries are the exception rather than the rule. But accidents do happen. Koo emphasizes that many of the action sequences that people assume are done with green screen are in fact happening in “real life,” particularly on big-budget movies. As a consequence, bruises, bumps, and sometimes serious accidents will occasionally occur. Lamb says she has suffered a broken clavicle, a blown ACL, and a broken back, but continues to return to the profession she loves after getting well. “Advil is our friend,” she says, as is a good masseuse. (Performers who agree to a particularly dangerous stunt often also receive a pay increase, known as an adjustment.)


Despite these risks, a stuntperson cannot afford to get nervous. “When you get nervous, that’s when you get hurt,” Koo says. His approach is to think through a stunt and then put any worries out of his mind. “I tell myself ‘that’s it!’ Don’t get nervous. Just do it.” That’s not to say that jitters don’t come into play sometimes. “I think all stunt performers get that nervousness like any other performer,” Kuhr says. He says multiple rehearsals are invaluable in cutting down on both nerves and risk.


Special padding is part of a stunt performer’s arsenal, but if you’re a woman it may not be an option. “Sometimes certain articles of clothing like skirts prevent us from wearing thicker pads or even pads at all,” Lam explains. “Sometimes a little improvisation is needed. My skinny jeans were so tight one time I used gel petals for knee pads.” Lamb alludes to instances of having to wear “just a towel to do a fight or a stair fall.” She adds that high heels can present another hazard, but since she has often doubled for “11-year-old boys or senior citizens,” she has mostly been able to avoid them.


Mack Kuhr with Keanu Reeves on set for John Wick 2. Image credit: Mack Kuhr 

When doubling for an actor, stunt performers have to do more than bear a passing resemblance: They must consider the actor’s physicality and movement, too. “It is truly an exercise in impersonation,” Lamb says. “You as the stunt double are there to merely match [the actor’s] action and then take over and honor their work as you get tossed out of a moving car.” This is particularly true when a young stuntperson is doubling an older actor. Lamb explains that older people tend to move differently, and often have a different center of gravity. She says she once coached a young actress who was doubling an older person falling to “think light and then go heavy like a noodle.” 


If you’re going to put your neck on the line for others’ entertainment, it might as well be fun. Fortunately, stunt performers say it often is—although their idea of joy might not match the rest of society’s. Lam describes squib hits, or onscreen gunshots, as particularly enjoyable. “I get to wear a mini blood packet that explodes when the squib guy presses a button,” she says. “The blood comes pouring out and there’s a big smoky hole in my shirt.” 

Koo describes working on car hit scenes with a budget as a bit like being a kid in a sand box. “It’s kind of like we’re demolition,” he explains. “They tell you: money is no object, don’t worry about wrecking stuff because it’s in the budget. You’re like a big kid that gets to break stuff.” Lamb expresses a fondness for stair falls, with her first-ever fall being a famous scene in the movie Fargo (1996). However, she admits her favorite stunts are “the kind that leave me in one piece.” 


Some of Kirby’s students include highly skilled martial artists hoping to apply their abilities to stunt and stage combat work. However, it’s not always helpful for a stunt fighter to fight as well as Bruce Lee, since the film’s stars are the ones who need to look the best and often win onscreen fights. “If you are lucky enough to get into that fight with Tom Cruise,” Kirby says, “you better be willing to suck.” 

Koo confirms this. “You don’t want to showcase your skill unless you’re the principal person that’s supposed to win that fight. You’re there ... to get beat up and thrown around, and that’s your job.” Lamb adds that she needed to set aside her gymnast’s ability to land gracefully in order to convincingly fall out of a window. “One of the things we need to do is to be sloppy and be ok with it,” she says.


Lamb explains that her decades of stunt work have infiltrated her daily life in certain ways, including how she views her physical environment. For instance, she often assesses sets of stairs in terms of how well they would work for a stair fall. “I might be looking through Real Simple or Architectural Digest and think ‘oh, those are good,’” she says. She also says that her work has influenced her parenting (or as she describes it, her role as a “stunt mom”) and imparted resilience to her children. “They do know how to take a tumble and roll right back up and keep moving.” 


Employability, for many stuntpeople, depends on developing new skills and perfecting old ones. Lam says she takes a variety of martial arts classes with the aim of becoming a more well-rounded fighter, and is training with a rope dart and chain whip—two traditional kung fu weapons. “The beauty of this industry,” she says, is that “it forces you to get out of your comfort zone and learn new things.” As a fight instructor, Kirby has the opportunity to observe many honing their craft. “The best people in this industry never stop learning,” he says.


In between jobs, stuntpeople keep fit and train frequently so that they will be able to “spring into action,” literally, at a moment’s notice. “You never know when the bat phone will call and it’s time to suit up,” Kuhr says. Stuntpeople may train at specialized gyms where they can learn from and work with other performers like themselves, or typical gyms. Kuhr’s regimen, which includes cardiovascular training (to help with constant sprinting on set), strength training, agility work, martial arts training, sparring, and good nutrition, is typical of many stunt players.


Stuntpeople describe their community as tight-knit, with bonds forged by unique experiences. The people in this high-risk profession look out for each other, both in terms of safety and when it comes to nailing a new stunt or developing new skills. “We all look out for each other and train together,” Lam says. “If I don’t know how to do something, there will be someone within the community who will lend advice. You teach me how to do a car hit and I teach you about affective memory in Method acting.”


Perhaps surprisingly, there is no Academy Award category for stunt work. (There are other awards, including some from the Screen Actors Guild and the Taurus World Stunt Awards.) Nearly all of the stunt performers interviewed here mentioned the lack of an Oscar for their work. A petition called Stand Up for Stunts is currently circulating to change that, and has received over 83,000 signatures so far.

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iStock // Ekaterina Minaeva
Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
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iStock // Ekaterina Minaeva

Jacques Mattheij made a small, but awesome, mistake. He went on eBay one evening and bid on a bunch of bulk LEGO brick auctions, then went to sleep. Upon waking, he discovered that he was the high bidder on many, and was now the proud owner of two tons of LEGO bricks. (This is about 4400 pounds.) He wrote, "[L]esson 1: if you win almost all bids you are bidding too high."

Mattheij had noticed that bulk, unsorted bricks sell for something like €10/kilogram, whereas sets are roughly €40/kg and rare parts go for up to €100/kg. Much of the value of the bricks is in their sorting. If he could reduce the entropy of these bins of unsorted bricks, he could make a tidy profit. While many people do this work by hand, the problem is enormous—just the kind of challenge for a computer. Mattheij writes:

There are 38000+ shapes and there are 100+ possible shades of color (you can roughly tell how old someone is by asking them what lego colors they remember from their youth).

In the following months, Mattheij built a proof-of-concept sorting system using, of course, LEGO. He broke the problem down into a series of sub-problems (including "feeding LEGO reliably from a hopper is surprisingly hard," one of those facts of nature that will stymie even the best system design). After tinkering with the prototype at length, he expanded the system to a surprisingly complex system of conveyer belts (powered by a home treadmill), various pieces of cabinetry, and "copious quantities of crazy glue."

Here's a video showing the current system running at low speed:

The key part of the system was running the bricks past a camera paired with a computer running a neural net-based image classifier. That allows the computer (when sufficiently trained on brick images) to recognize bricks and thus categorize them by color, shape, or other parameters. Remember that as bricks pass by, they can be in any orientation, can be dirty, can even be stuck to other pieces. So having a flexible software system is key to recognizing—in a fraction of a second—what a given brick is, in order to sort it out. When a match is found, a jet of compressed air pops the piece off the conveyer belt and into a waiting bin.

After much experimentation, Mattheij rewrote the software (several times in fact) to accomplish a variety of basic tasks. At its core, the system takes images from a webcam and feeds them to a neural network to do the classification. Of course, the neural net needs to be "trained" by showing it lots of images, and telling it what those images represent. Mattheij's breakthrough was allowing the machine to effectively train itself, with guidance: Running pieces through allows the system to take its own photos, make a guess, and build on that guess. As long as Mattheij corrects the incorrect guesses, he ends up with a decent (and self-reinforcing) corpus of training data. As the machine continues running, it can rack up more training, allowing it to recognize a broad variety of pieces on the fly.

Here's another video, focusing on how the pieces move on conveyer belts (running at slow speed so puny humans can follow). You can also see the air jets in action:

In an email interview, Mattheij told Mental Floss that the system currently sorts LEGO bricks into more than 50 categories. It can also be run in a color-sorting mode to bin the parts across 12 color groups. (Thus at present you'd likely do a two-pass sort on the bricks: once for shape, then a separate pass for color.) He continues to refine the system, with a focus on making its recognition abilities faster. At some point down the line, he plans to make the software portion open source. You're on your own as far as building conveyer belts, bins, and so forth.

Check out Mattheij's writeup in two parts for more information. It starts with an overview of the story, followed up with a deep dive on the software. He's also tweeting about the project (among other things). And if you look around a bit, you'll find bulk LEGO brick auctions online—it's definitely a thing!

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Cs California, Wikimedia Commons // CC BY-SA 3.0
How Experts Say We Should Stop a 'Zombie' Infection: Kill It With Fire
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Cs California, Wikimedia Commons // CC BY-SA 3.0

Scientists are known for being pretty cautious people. But sometimes, even the most careful of us need to burn some things to the ground. Immunologists have proposed a plan to burn large swaths of parkland in an attempt to wipe out disease, as The New York Times reports. They described the problem in the journal Microbiology and Molecular Biology Reviews.

Chronic wasting disease (CWD) is a gruesome infection that’s been destroying deer and elk herds across North America. Like bovine spongiform encephalopathy (BSE, better known as mad cow disease) and Creutzfeldt-Jakob disease, CWD is caused by damaged, contagious little proteins called prions. Although it's been half a century since CWD was first discovered, scientists are still scratching their heads about how it works, how it spreads, and if, like BSE, it could someday infect humans.

Paper co-author Mark Zabel, of the Prion Research Center at Colorado State University, says animals with CWD fade away slowly at first, losing weight and starting to act kind of spacey. But "they’re not hard to pick out at the end stage," he told The New York Times. "They have a vacant stare, they have a stumbling gait, their heads are drooping, their ears are down, you can see thick saliva dripping from their mouths. It’s like a true zombie disease."

CWD has already been spotted in 24 U.S. states. Some herds are already 50 percent infected, and that number is only growing.

Prion illnesses often travel from one infected individual to another, but CWD’s expansion was so rapid that scientists began to suspect it had more than one way of finding new animals to attack.

Sure enough, it did. As it turns out, the CWD prion doesn’t go down with its host-animal ship. Infected animals shed the prion in their urine, feces, and drool. Long after the sick deer has died, others can still contract CWD from the leaves they eat and the grass in which they stand.

As if that’s not bad enough, CWD has another trick up its sleeve: spontaneous generation. That is, it doesn’t take much damage to twist a healthy prion into a zombifying pathogen. The illness just pops up.

There are some treatments, including immersing infected tissue in an ozone bath. But that won't help when the problem is literally smeared across the landscape. "You cannot treat half of the continental United States with ozone," Zabel said.

And so, to combat this many-pronged assault on our wildlife, Zabel and his colleagues are getting aggressive. They recommend a controlled burn of infected areas of national parks in Colorado and Arkansas—a pilot study to determine if fire will be enough.

"If you eliminate the plants that have prions on the surface, that would be a huge step forward," he said. "I really don’t think it’s that crazy."

[h/t The New York Times]