Ballistic: Chapter 12

It's gotta be the shoes

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Chapter 12 is an interesting one. We have a sense that the sneaker companies spend a lot of money on research, and maybe we assume a lot of that money goes to injury prevention and improved athletic performance. But once P3 founder Marcus Elliott, M.D., and P3 president and head of biomechanics Eric Leidersdorf got really deep into the movement data, they found that science had a hard time entering the shoe design conversation. Please enjoy Chapter 12 of Ballistic, which you can learn more about here.

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Illustration by John Early.

Ten Millimeters from Nowhere

Begin at the beginning and go on till you come to the end; then stop.

—­Lewis Carroll

On Eric’s computer screen, James Harden’s feet stabbed the ground. Eric rolled the video back and forth, as the accompanying rows of data delivered a mixed bag of insight. Most days, Eric’s corner of P3 is as dry as toast, but on this day in 2016, things were a touch more glamorous. Not only did Harden himself sit two yards away, but also milling around were a handful of people who arrived with him, maybe a dozen more from Adidas and Adidas’s ad agency. Harden was the best scorer in the NBA; everyone seemed certain P3’s assessment would unveil exciting news of his athletic perfection.

The problem was, Eric had promised a little in-­person preview of Harden’s full results, and on his screen the data did not match the mood. “He’s not,” Eric says looking back, “winning a dunk contest.” Compared to the NBA players in P3’s database, Harden was “pretty average for his position,” Eric says, “or slightly below in some respects.”

Huh. Eric’s mind danced. Harden had eluded the finest athletes on the planet, night in and night out, for years. Clearly, he could move. What were they missing?

Eric thought about how Harden’s game was heavy with things P3 had never tried to measure: hand-­eye coordination, shifty movements, reading the floor, and shooting. He’s a master of getting opponents and referees off balance. Would that be enough to overcome mediocre athleticism?

Then Eric’s brain made a conceptual leap—­from a Houston Rocket to rockets in general. When a SpaceX rocket takes off, a crowd assembles outside the glass wall at mission control. They count down the launch sequence and burst into applause when the rocket ascends with a cloud of steam and dust.

But they’re really waiting for the booster to return. “We used to just dump them in the ocean,” says Eric. Now, as the SpaceX booster descends, the robot-­driven engines fire up. “There’s a big vertical acceleration,” says Eric, “just shy of gravity.” Instead of crashing into the launch pad, the booster hovers to rest like the emperor’s ship arriving on the Death Star. In the final seconds, mechanical arms fold down and it parks, looking majestic. That’s when the crowd goes crazy.

Bodies don’t have jet engines that fire while landing. But they do have the eccentric movement of muscles. We think of muscles contracting—­shortening, sometimes called “flexing”—­which is what they do when we jump. Eccentric movement, on the other hand, is lengthening muscles under control. The force produced in eccentric movements slows you down in a controlled way, effectively pushing up, just shy of gravity, as the body comes down. “It’s a physical quality,” Eric remembers thinking, even if it’s not a physical quality historically prized by All-­Stars.

P3’s general manager, Adam Hewitt, had prepared the team for Harden’s visit with a dossier that showed, among other things, that Harden led the league in stepbacks. That’s where Harden drives forward, gets the defense to worry he might keep going, and then stabs a foot into the floor, pops backward, and rises to shoot. It’s a shot that works because Harden can change from forward to backward faster than the defense.

As a thing to unfurl to the assembled group, it wasn’t too exciting, perhaps—­but it was the truth. The secret of being James Harden, Eric nervously told James Harden, was something almost no one in basketball cared about: stopping on a dime.

Amazingly, the Adidas people loved it. “They really ran with it,” remembers Eric. “Their excitement helped encourage us.”

Eric says P3 then “actively started to look for, and studied, and tried to formalize” the biomechanical definition of what they call “decel,” for deceleration.

Once they had defined the movement, P3 found elite stoppers everywhere: basketball, volleyball, football, soccer, and NASCAR pit crews. The data suggested that players with good brakes had meaningful advantages across sports. The data had coughed up a movement super-­skill.

Decel is not assessed at the combine, it’s not part of scouts’ standard vocabulary, it’s seldom mentioned on TV broadcasts. But it matters. With brakes as his only elite physical quality in P3’s assessment, Harden won the NBA’s Most Valuable Player Award the following season.

Just as Eric started to really dig into the concept of brakes, a seventeen-­year-­old Slovenian basketball player came to P3 for assessment while his mom sat on the couch. His data turned out to be a lot like Harden’s: didn’t jump, run, or cut especially well. But dang, could he stop.

That’s interesting, thought Eric. Let’s see how this guy’s career goes. Luka Dončić quickly became the youngest MVP in the history of European basketball, an NBA lottery pick, and a perennial NBA MVP candidate. Other P3 All-­Stars, like Zach LaVine and Darius Garland, tested with great brakes as well.

Suddenly, decel was a thing athletes wanted to learn, which gave Marcus a reason to get the whole P3 staff reading Verkhoshansky. There are two big advantages to training brakes with plyometrics. The first is that it grooves the feeling of a strong landing, upping the odds that it will be deployed in a game. The second is that it gets you moving into the next jump. Even in gymnastics, after flying off the uneven bars, you land, bend knees, then stand. In football, when you throw out a leg to brake, you then want to escape the cornerback with your next move. In basketball, when you step back, you want to jump into a shot. Jack explains that Verkhoshansky researched this exact thing, and “he found that if he just did the braking portion, but didn’t couple it with some sort of concentric output afterwards, it actually robbed them of the natural movements you want to see.”

Once their lower legs, and landing form, are strong, P3 trainer Jack says, he has players jump from a high box and explode into other movements. “There is no bigger eccentric stimulus we could give them,” says Jack. By design, it’s a recipe for big forces and a short amount of time. If the form is sloppy, that’s precisely how injuries occur. With good biomechanics, however, those same ingredients inspire elite athleticism.

P3 has other ways to pump the brakes. Just as muscular tissue can be trained to shorten faster and more forcefully to lift an athlete off the ground, so can muscles be trained to elongate with strength against great forces.

For experienced weight lifters, the move involves an absurd, bar-­bending amount of weight across the shoulders—­quite literally, more than you can lift—­and lowering it under control. The various techniques to end this kind of movement, one of which is simply ditching the bar, all require serious technique, which is why P3 never does overloaded eccentric squats with NBA players. “None of these guys,” Jack says, “are great lifters.”

A P3 workaround: Athletes hold a dumbbell in each hand, facing a box. Then, with deft timing, they dip down for a jump, ditch the dumbbells to the floor, and leap onto the box. It’s a jumping exercise with weight added only in the eccentric approach phase. That adds training work, and puts a helpful stretch into the jumping muscles. Amazingly, the most common result is that players jump higher than with no weights at all.

Another favorite is a gizmo called the kBox, which looks like a high-­end air fryer. In the most basic movement, you stand on the flat top of the kBox with a cable running to a harness around your torso. Then you squat. The kBox is different than pumping iron, however, because the resistance comes from a flywheel that sticks out the front of the machine. It’s like winding and unwinding a massive yo-­yo. The cable builds huge down-­pulling forces you need to resist, but then reaches the end of its range, stops spinning, and then unwinds in the other direction, freeing you to stand back up. But you want to be thoughtful about that, too, because you’re winding the thing for the next rep. “The faster I pull up,” Jack says, “the harder it pulls down.”

P3 coaches have found they can achieve about a 6 percent improvement in NBA player braking over six weeks. Players loved their new stopping speed. Adidas loved the new marketing message. The Harden Vol. 1 shoe launched in 2016 with a press tour that touted a “data-­driven” pattern in the rubber of the sole, and the shoe included a rubber wrapper around the toe to keep your foot from flying forward when braking hard. It was positioned as a stopping machine.

But can a shoe really help you move better?

One April day in 2013, on an out-­and-­back of the Rutgers Unite half-­marathon, I watched the lead pack scream past in the other direction. A man named Demesse Tefera seized the lead in a freewheeling way that moved me to scream, “HELL YEAH!” across the road. I pumped a fist, felt a rush, and sliced about three minutes off my personal best.

I can still hear the allegro cadence of his feet, alighting briefly and beautifully on planet earth, defying physics’ technical term for the event: a collision.

In physics, there are two kinds of collisions. Elastic collisions involve no loss of kinetic energy. Picture billiard balls—­one hits another, which departs at almost the speed of the first. Inelastic collisions get you a failing grade on the egg drop, because kinetic energy is lost and the objects slow down abruptly. Inelastic collisions tend to be hot and loud—­the textbook example is a head-­on truck accident. When Katie Spieler landed on her heels, it sounded like a sack of bricks and the force plates registered the impact of an angry bighorn sheep. (Related: “I heard a pop,” people say, of tearing an ACL.)

The April footfalls of Demesse Tefera were barely detectable. He deployed some of humanity’s best landing gear. Strong quads absorb huge forces, as do—­in ideal running form—­the soleus, glutes, gastroc, and hamstrings. Brilliantly, this system also stores those forces and can use them to spring forward again. Tefera’s legs acted like rubber bands, pushing him forward with a blend of his own active work, and the residual freebies carried over from the last step. Tefera’s footfalls were about as close to elastic as a foot-­ground collision can be.

Tim Noakes’s classic book The Lore of Running says up to 93 percent of the force of landing can be redeployed into the next step. Runners in cushioned shoes, however, pass along about half that. There’s a chicken-­and-­egg question about whether we need soft shoes because we are bad at managing big forces, or we are bad at managing big forces because we wear cushioned shoes.

Harvard research led by Daniel E. Lieberman, Ph.D., finds that “habitually barefoot or minimally shod humans tend to walk and run differently than shod people, often in a way that leads to very low collision forces, even on very hard surfaces.” After a lifetime in shoes, Lieberman began running barefoot around paved Cambridge, pointing out that, evolutionarily, it’s wearing shoes that’s weird.

What seems to be happening is that the relatively small amount of padding in a shoe sole makes it feel safe to land on toes, heels, or any old place. But humans are heavy eggs and that rubber is thin, with a minuscule fraction of the shock-­absorbing powers of Demesse Tefera’s collection of springy muscles. Without the body in a good position to deliver the landing forces to the quads and glutes, the landing becomes inelastic, like the truck crash in the physics textbook. And remember how crashes make noise? They also emit heat. Noakes writes that “the remainder of the energy heats up the midsole.”

Think about it: you’re killing yourself to move forward, and a good chunk of the force you’re creating is being lost to the silly side project of simmering your expensive shoes. Imagine a Formula One racer losing power to a toaster oven in the cockpit.

There’s precious little academic research on basketball shoes and safety, but a 2017 article in Lower Extremity Review quotes an academic as saying shoes “can definitely make things worse.” Describing a 2022 survey of running shoe studies by Cochrane Reviews, the New York Times’s Cindy Kuzma wrote, “the analysis found no evidence that running shoes, or prescribing certain shoes by type, have injury-­preventing properties.”

Shoe companies frequently commission P3 to consult. But to P3, biomechanics often feel like an afterthought in those discussions. “They’ll draw up something they think looks really cool, in quite a bit of detail. And they’ll say that’s gonna be Ant Edwards’s shoe and then they will have their tooling guys make it. And it’s really starting from the outside in,” Marcus says. “It’s done with the premise that they have to build something that’s cool to sell to millions of kids. And I get that.

“But I just keep saying you’ve got to start with functionality. You got to think of Ant Edwards as this amazing machine, and you’re going to build some tool for that machine that’s going to make the machine work better.” On the day we spoke in 2024, Marcus had just visited Adidas in Portland, Oregon, where he says he pitched an entirely new way to design shoes, which would mean having the best players in the world move around on P3’s force plates in several different prototypes, while Eric’s team assessed to see which, if any, offered movement advantages.

If that process produced an athletic shoe with a real, demonstrable performance advantage, it might be the first of all time. Marcus and P3 have a front-­row seat on how shoe company research money is spent; some of it is spent at P3. Marcus is surprised at how seldom P3 is asked to look into the big questions of sports, like how injuries correlate with shoe design, what body type is best in which shoe, or whether shoes change how athletes move. Marcus says, “They’re mostly about colorways and design features.”

In the Lower Extremity Review article, representatives of the major shoe companies tell writer Will Carroll that when shoe companies call a shoe “custom” to a player, that doesn’t mean it was designed for his foot. It means the player told the shoe company what color and level of cushioning he likes. What tends to happen is that players like something that the shoe-­buying public also likes: that squishy-­cushion feeling when you try it on. (“It’s like sex on your feet,” Joakim Noah once told me about the Boost material in his Adidas, at an Adidas promotion event, sharing a couch with the Adidas CEO.)

Noakes calls athletic shoes an “expensive gimmick” in need of an infusion of hard-hitting research. “Perhaps,” writes Noakes, “just as the pharmaceutical companies must expose their drugs to extensive testing before they may be released for use by the general public, the time has now dawned for running shoes to be subjected to similar considerations.”

Meanwhile, you know who wins a laboratory treadmill test, running as fast as Usain Bolt’s world-­record hundred meters thirty times in a row, up an 11 percent gradient? A pronghorn antelope, that’s who. And they run on goddamned hooves. (This actually happened. Scientists put pronghorns on treadmills.)

The best athletes P3 has ever tested were not antelopes, but they did have something in common with them: instead of needing protection from the force of landing, they used the landing collision to begin the next bounce. Demesse Tefera and Usain Bolt know that human bodies can carry energy from one movement into another without cooking our soles or making loud slapping sounds.

Unfortunately, in that project, shoes often get in the way. Equipment-­wise, basketball doesn’t take much. All anyone really needs to ball, besides a ball and a hoop, is sneakers. The cost of shoes is nothing compared to a bag of hockey equipment or a set of golf clubs. But it’s enough that the athletic sneaker industry generates about ten times the revenue of all the teams of the NBA combined.

Yet, every day, P3 staff asks athletes to take off their shoes for certain parts of the workout because wearing shoes might increase the likelihood of catastrophic injury. NBA All-­Star Khris Middleton has worn Nikes since college, but at P3 he does trap bar dead lifts with no shoes at all. Major League Soccer’s Juanjo Purata does aggressive hip flexor work against the resistance of the cable machine in black socks. When the WNBA’s Haley Jones slipped a green exercise band around her foot before a predraft hip exercise, her shoes were on the floor by the couch, next to her phone.

Marcus often rants about footwear. His first concern: athletic shoes tend to have a ten-­millimeter drop from heel to toe. “No one,” says Marcus, annoyed, “can tell you why it’s ten millimeters. There’s no magic about it. Lifting somebody’s heel, you affect lots of mechanics—­more in crappy ways than in good ways.” Certain kinds of weight-lifting shoes have elevated heels to allow for deeper squats, but other than that, P3 sees no benefit to elevated heels.

In fact, they see danger. Elevated heels encourage people to land toes down. At slow speeds, that increases forces running through the knees. In big, explosive movements, that “puts their knees in a dangerous position,” explains Marcus.

Marcus notes that some of the edgier running companies have sold zero-­drop shoes since Born to Run. “I’ve been advocating this,” Marcus says, “for a long time.” Though Marcus, like many athletes, has an extensive collection of standard ten-­millimeter drop shoes, he often wears zero-­drop shoes, or Birkenstocks. He says he’s happiest barefoot. (After a summer trip to Venice for the Biennale, a citywide art exhibition, Marcus reported loving the people, the setting, the food, and the fact that “I did everything barefoot.”)

Marcus may not be able to tell you why basketball shoes have a ten-­millimeter drop from the heel to the toe, but Dave “Boot” Bond can. Bond was the director of basketball at Nike when they created the Jordan, Pippen, and Barkley signature shoes. He wrote the original business plan for the Jordan Brand and hired the team that launched it. He has played similar roles at Adidas, Anta, Quiksilver, and UnderArmour.

“I’ve spent my career in the athletic footwear industry,” Bond says. “I got to work with pretty much the entire Dream Team, including Michael Jordan. We made his shoes. That was high stakes! Making footwear for the world’s most famous athletic person. You couldn’t goof around and make things that just look good.”

In the explosive early days of athletic shoes, though, there was a gimmick that reliably moved product: a pocket of air in the heel. “Back in the day,” Bond says, artfully avoiding naming a company, “you had to fit a visible air bag and had to make room to fit a technology. It became the standard look and silhouette of a basketball shoe.”

That, Bond says, is why athletic shoes have a ten-­millimeter drop.

A fixed height in the back, Marcus says, means the same model of shoe has a low slope for Shaquille O’Neal, who wears size 22, and a steep slope for a small child. “Those are totally different angles, different dynamics, different physics,” says Marcus. “How can they both be right?”

Bond says that there’s “no scientific basis for it.”

In 2006, Bond joined K-­Swiss in Los Angeles, where his first big project centered around eye-­poppingly athletic French tennis player Gaël Monfils. Monfils made highlights leaping, cutting, and murdering the ball in exciting ways. “Somebody told me,” Bond remembers, “about some guy in Santa Barbara doing cutting-­edge biomechanics with athletes. They told me all about him, and I am stupid that way—­I just drove up there.”

Bond walked into P3 with no appointment. Before long, Monfils was in Santa Barbara, too. In 2011, K-­Swiss had a hit with the Big Shot shoe featuring something called a “Ballistic Propulsion Plate” under the ball of the foot. Marcus still has a Big Shot in his office, complete with a P3 logo on the outside.

What Bond remembers most is the first time Marcus really unfurled his cavalcade of sneaker industry complaints. “He was never mean,” Bond says, “just frustrated, having to take athlete’s new shoes off, to put more generic shoes on them to do testing. The products were going in the wrong direction, he said.

“Of course, he blamed me for the entire industry. So, I said first of all, ‘I didn’t do that.’ And second of all, ‘What would you do, smartypants?’

“He said, ‘Your industry doesn’t realize that force is your friend.’ The force that an athlete generates landing—­great athletes use that force.”

Bond was sold. In June 2016 Sports Illustrated featured Marcus and Bond’s new shoe brand, Ampla. The running shoe featured a carbon-­fiber plate in the sole. “The model when building running shoes has been that force is your enemy, this the opposite model,” Marcus told SI’s Tom Taylor, who wrote that “Elliott wants to redirect the force, not squish it into a wedge of foam.”

It was halfway to a pronghorn hoof, and inspired by the blades worn by amputee sprinters.

Marcus wanted it even springier. “I wanted to start with a pogo stick,” he says, looking back, “and then just tune it down a little.” At the end of the SI story, Bond says something that sounded kooky in 2016: he hoped this kind of carbon-­plate running shoe technology would lead to someone breaking two hours in the marathon.

Marcus still wears an Ampla hat to work sometimes, and an Ampla shoe is one of the three or four “decorations” in his bare-­bones office. But the shoe hit the market with terrible luck: Ampla’s parent company, the surf brand Quiksilver, declared bankruptcy in September 2015. Bond, Marcus, and a couple of other investors bought the rights to Ampla. Bond rented an office in Los Angeles, where he personally processed and shipped the orders as they came through the website.

“We sold about a thousand pairs,” says Bond. “Nike’s head of innovation bought, like, twenty pairs. A few years later, they come out with the sub-­two marathon shoes, which are ridiculously similar. We started a conversation in our industry about hyper­performance. They took the germ of an idea and really spread it. I would say Marcus is one of the inspirations for carbon-­plated shoes. He wanted shoes to be not mushy and soft, but spring-­loaded.”

On the feet of Kenyan distance runner Eliud Kipchoge, Nike’s carbon-­plate shoes lit the record book on fire. At the 2018 Berlin Marathon, Kipchoge broke the world record by a minute and eighteen seconds, with a time of 2:01:39. In 2019 in Vienna, assisted by a team and a pace car that invalidated it as a world record, Kipchoge broke two hours, running a once-­unthinkable 1:59:40. In 2022 he took another thirty seconds off the world record.

Running shoes with carbon-­fiber plates have created such a tectonic shift that legendary runners like Kara Goucher and Des Linden spent an hour of their podcast explaining why records from before carbon plates are no longer relevant. Times have fallen in every event. Goucher likens shoes with carbon-­fiber plates to doping.

One measure: in the fifty-­seven years after Jim Ryun became the first high-­schooler ever to break four minutes for the mile, another high-­schooler ran that fast, on average, every 4.75 years. In 2022, when “super shoes” hit the scene, six different high-­schoolers shattered the barrier.

The running shoe market, with carbon fiber and an array of zero-­drop options, is showing signs of evolution. Basketball shoes, on the other hand . . .

“There are a handful of flat-­to-­the-­ground running products,” Bond says, “but the whole barefoot movement in running never made it over into basketball.”

“They’re not as comfortable,” says Bond, “and they look weird.” Basketball shoe purchasers, Bond says, “want performance right up to the point it doesn’t look weird. These shoes are bought by kids, literally twelve-­ to twenty-­year-­olds. If you’re beyond twenty and playing basketball, you’re old.”

Bond joined UnderArmour in 2018 and says, “The Curry 8 and 9 are heavily Marcus-influenced, even though he doesn’t know it. I consider myself a disciple of P3 and I’ve applied those things. Those are probably the most P3-­centric shoes on the planet. They’re not completely flat—­there’s a six-­millimeter heel lift, I believe. So, it’s 40 percent closer to the ground than most.” Bond says Curry had a career resurgence around the time he started wearing them, then adds, with a laugh, “I’m not going to take all the credit.” That’s not to say the shoe industry has truly applied the lessons of biomechanics generally. Eric works alongside Sloan Hanson, a biomechanist who grew up playing soccer and working out at P3. Sloan studied data at Berkeley, and now enjoys exploring how shoe models correlate with injury in the NBA. Some of his early work found that three models made under one of the biggest athlete-­name brands led the league in injuries per game in 2023–­2024.

“Because we have so much data on some of these athletes, we could actually start looking at some of those patterns, their movement patterns, associated with guys playing in Kobes versus LeBrons. They should know these things, right?” Marcus says. “They should know if [any particular shoe] decreases your risk of injury or increases your risk of injury.”

In P3’s assessments, Marcus feels like he sees players moving in unnatural ways that would have never developed if they had grown up barefoot, or in very different shoes. “When guys do slides in our facility,” Marcus says, “they stomp on their shoe when they change directions. They treat it like it’s a big berm.” Baked into thinking about basketball shoes is the assumption that the foot lands on a squishy platform, and then, Marcus says, “you try to figure out how to keep the foot attached to the platform.” But what if, instead, he asks, “you made shoes that were more wrapping the foot?” Would basketball players move like ballet dancers? Would basketball players, Marcus wonders, land, cut, and jump in ways where “your foot is still operating like a foot”?

Trent Reeves is a biomechanist, not a shoe designer, but he did work at one major shoe company for a year and he joined many of P3’s meetings with other shoe companies. “My experience in footwear has been [that they design footwear] kind of backwards,” Trent says. If a shoe company has some technology that’s selling well, he says, using that becomes the mandate, rather than asking how a shoe might, say, prevent ankles from rolling inward.

The P3 ideal would be for shoe companies to start with some performance or injury-prevention goal. Eric has poked around in the data already on P3’s servers. “Talk about low-­lying fruit,” Eric says. “If they wanted to get serious, there’s a lot that could be done.”

Should different people have different kinds of shoes? Marcus points out that there are special shoes for male guards and for male big men, but there isn’t a single basketball shoe designed for a woman. “Women’s shoes,” he says, “are small men’s shoes.” The most-­worn shoe in the WNBA is a Kyrie Irving model. How, I wonder, would Marcus make shoes differently for women? “That,” Marcus says, “is what we need to find out!”

“At some point,” Eric adds, “it will really benefit the world’s greatest athletes to put ’em in shoes that really suit them.” P3 already sorts athletes by categories that emerge from studying movement patterns, performance, and injury risk. It would surprise no one at P3 if the right answer proved to be shoes designed not for guards, big men, or women, but athletes who land with toes down, in translation, or with feet that tend to rotate on landing.

One shoe design for everyone feels, to Marcus, long outdated. Breast cancer researchers are decades into seeing that survival improves dramatically when you dig into the specifics of each case—­HER2, hormone-­sensitive, there are dozens of varieties that suggest very different therapies. Studying all cancer patients together, as a monolith, would obscure the most effective remedies. Marcus suggests the same will prove true for athletic shoes. “This old analytical model we have of just aggregating data and seeing what the net effect is, misses so much signal,” he says. “That’s true in drug discovery, surgical interventions, poverty studies. So, without question, there are some people that are going to be much more dangerous running in a minimalist shoe. They need some things that a cushioned, lateral stability–­based shoe can provide. They basically need some help.”

In 2017, big footwear companies announced they would scan individual runner’s feet and then build shoes for them in “fast factories.” But pretty soon, Marcus says, “they realized that they didn’t know what questions to ask to build a shoe for you. Other than get a 3D scan of your foot.” Once again, it was the problem of a static scan versus a study in motion. Robots might be able to solve the relatively simple problem of making a shoe, but they couldn’t solve the wicked nuances of human movement.

“What about your system? Where do you need help? You know, how are they going to optimize you to reduce the risk of injury?” Marcus says. “I was super-­excited about it, and then I realized that they . . . had the technology to build it, but they were not actually very close to having any knowledge to build it.”

Meanwhile, basketball players don’t have much choice. Trent is the star of P3’s local rec-­league championship-­winning team. I ask him what he plays in. “I play in Dellys.” (Did you know that longtime NBA role player Matthew Dellavedova has a signature shoe?) I asked why. “Because he’s a really cool guy,” says Trent. “Because he came in and we trained him for a while and he was nice enough to give us some comps. And so I got his Santa Clara version of the shoe. But yeah, it’s funny: when I play basketball and put on a pair of basketball shoes, like the brain, the science brain kind of turns off a little bit and it’s just, like, ‘These feel good. I’m gonna play in these.’ ”

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