Baseball’s Next Great Analytical Frontier

Mariano Rivera was never secretive about the grip on his signature pitch. He’d show it to teammates, coaches, even reporters. He placed his index and middle fingers together along the seams. He pulled down with his middle finger upon release. The ball would whiz arrow-straight before veering sharply a few inches from where the hitter expected it.

When teaching pitchers how it should feel coming out of their hand, however, Rivera could be frustratingly vague. Put pressure on the middle finger, he would say. This can be a moneymaker for you. Even now, nobody can make a fastball move quite like Mo’s. “It is as if it dropped straight from the heavens,” he wrote in his 2014 memoir. “How can I explain it any other way?”

Eleven years after Rivera’s retirement, a wrist brace with claws could strip any last intimation of divinity out of pitching. A pitcher’s fingers slide into its four rubber rings, attached to metal straws that are fastened by a Velcro strap around the wrist. This device, the FlexPro Grip, measures exactly how quickly each of a pitcher’s fingers exert pressure on a ball. But the point of the gadget isn’t just to register finger forces. It’s to transform the art of pitching into a science.
One afternoon last year, at a training facility called VeloU, I watched as Aidan Dolinsky, a pitcher for New York University, slipped on the FlexPro Grip and awaited instructions from Adam Moreau, the device’s co-creator. “I want you to squeeze with your two fingers”—the index and middle—“but only at about 50 percent of your maximum pressure,” Moreau said. “Hold it there for a few seconds. Hold, hold. And then instantly—boom—ramp up to your max force.”
As Dolinsky squeezed, Moreau began peppering him with numbers. “Get to 69,” he said, glancing at the app in front of them, “and then when you see that little green dot there, slam on it … Okay, hold, hold, go!”

The young pitcher needed a few tries before he mastered the proper sequence of acceleration. “I realized I was squeezing too hard, so then I backed off too much,” Dolinsky said.

“That’s quantifying feel!” Moreau cried. Imagine, he said, standing on the mound, and knowing exactly how much force to put on each key finger, and exactly how to peak them at the same time. “What would that do to your spin?”

Today’s professional pitchers throw harder than ever, but their art is still largely dictated by speculative notions of feel. Pitchers have forever been licking their fingers and clutching rosin bags to help with grip; these days, camera technology and data analysis have put a premium on players who can also impart enough spin to make the ball run, ride, cut, carry, sink, tunnel, and bore along a split-second flight path. It’s not enough to be blessed with a golden arm. You need to have it work in conjunction with your fingers, too.
Only recently, though, has anyone tried to understand exactly how those fingers work in pitching. In 2017, Glenn Fleisig, an expert in biomechanics, led a cohort of researchers looking at how elite pitchers apply finger pressure while throwing. By stuffing a regulation baseball with sensors, the researchers found that the force of the middle and index finger on the ball spiked twice, the last coming roughly six to seven milliseconds before release—in essence, the instant the ball leaves the hand. The force of that final peak averaged 185 Newtons, exerted through two fingers kissing the seams of a five-ounce baseball. It’s enough force to heave a bowling ball about 90 miles an hour.

When I spoke with Fleisig, he recalled that the primary motivation around the study was injury prevention. Elbow tears are collectively a billion-dollar problem for Major League Baseball each year, and “knowing how hard someone grips has implications about what’s happening in your elbow,” he said. What he found, though, also unlocked a mystery about pitching. Fleisig had previously reported that the angular velocity achievable by a pitcher’s shoulder maxes out at about 90 miles an hour, but pitchers can throw faster than that. Something else had to be providing that extra oomph—the fingers. “A huge thing that separates a good pitcher from a great pitcher,” Fleisig said, “is their ability to do that last push.”

[Devin Gordon: Arms are flying off their hinges]

Fleisig’s work is emblematic of a recent and long-overdue boom in touch research. “We’re now catching up to where we’ve been for many decades in the auditory and visual fields,” David Ginty, a neuroscientist at Harvard Medical School, told me. When Ginty started his somatosensory research lab in the mid-1990s, the field was small and quirky, dominated by a few labs producing a handful of papers a year. Today, the IEEE World Haptics conference, the top symposium where touch researchers share their findings, is a sprawling, festival-like event, sponsored by a subsidiary of Meta. Advancements in molecular-genetic techniques have enabled labs like Ginty’s to see how individual nerve cells respond to certain stimuli. It’s given researchers the best picture yet of the basic biology of touch, and it’s jump-started investigations into new treatments for chronic pain, anemia, irritable bowel syndrome, traumatic brain injury, and even low bone density. A stream of studies in recent years has also highlighted the psychological, cognitive, and creative benefits of doing things by hand.

In science, the closer anyone looks at touch, the more its influence becomes apparent. In baseball, it could revolutionize how teams look for the next Mariano Rivera with the magic feel.

For Connor Lunn’s entire baseball career, “feel” was waved off as something subjective and abstract, mostly because it couldn’t be measured. Eventually, Lunn, a recently retired minor-league pitcher, realized that people weren’t even trying. “We have every other metric out there—how hard you’re throwing, all the spin rates, the tail axis, everything,” Lunn told me. “But there was nothing out there on where you’re gripping the ball.” Learning how to throw a new pitch was like getting a prescription for eyeglasses based on what somebody else is telling you looks clear for them. In April, shortly before being signed as a free agent by the Tampa Bay Rays, Lunn was co-awarded the patent on a design for a baseball wrapped in a pressure-sensing fabric.

Alex Fast, a data analyst and writer for PitchingList.com, also thought the role of pressure was being overlooked. In March 2023, he gave a talk at the MIT Sloan Analytics Conference in Boston about measuring finger pressure in baseball. Using sensors and other supplies bought from Amazon, he built a feedback device that was tiny and flexible enough to be worn underneath a piece of tape on the fingertip and that could transmit force data to a microcontroller, worn inside a fanny pack on the pitcher’s lower back. “When I first got into analytics, I remember thinking that they’ve quantified everything,” Fast told me. But so many people that he spoke with after the conference shared his hunch about finger force, Fast told me later, that he began to think, This could be pitching’s next great analytical frontier.

[From the July/August 2023 issue: Moneyball broke baseball]

Part of what’s so notable about the attention being paid to touch in baseball circles is its contrast with how most of us navigate the world. I can point to one tool I reliably touch in my daily life: my iPhone, with its flat, smooth surface. I tap, scroll, and occasionally pinch it; calling it a touchscreen is an insult to the various forms of touch humans once used to manipulate pens, books, Rolodexes, keys, cash, coins, camcorders, calculators, discs, tapes, and credit cards. In households around the world, voice assistants and smart devices already respond nimbly to vocal commands to turn on lights, play songs, set temperatures, and change television channels. Hands-free fixtures fill the bathroom. Telehealth visits replace physical exams. Virtual reality has barely any use for the hands or feet.

That our grip on the physical world is slipping has real consequences: A long history of medical study has connected hand strength to overall physical health and longevity, for reasons that still aren’t entirely clear. Christy Isbell, a pediatric occupational therapist at East Tennessee State University, said she sees some kids as old as 4 or 5 years who have never held a pencil or a crayon. The absence of that tactile experience may change how they learn to read and write, she told me, and limit them in other ways. Healthy young adults who spend lots of time on their smartphones have weaker grips, duller fingers, and higher rates of hand and wrist injuries than their peers who use their phones less frequently. Professors at medical schools are raising alarms about the diminishing dexterity of surgical students.

Pitchers are an outlier. Unlike the rest of us, they must be attuned to precisely how their fingertips interact with the world every time they take the mound. And simply paying a little more attention to that interaction appears to make a great difference. According to research by the company that manufactures the FlexPro Grip, pitchers who use the device have been able to increase the rate of spin on their fastball by about 4 percent. A higher spin rate on a fastball can produce a “rising” effect that makes it harder for hitters to square up.

[Read: The scourge of ‘win probability’ in sports]

Even if the rest of us never get our finger pressure measured, the research is clear that we can benefit emotionally, cognitively, and physically by doing more with our hands—by jotting down notes, knitting, or taking a pottery class. With that effort, and the help of a few committed baseball buffs, perhaps we can arrest our collective drift into a hands-free world.