The conversation around baseball hitting mechanics has changed considerably in recent years, with the popularization of tracking data for exit velocity and launch angle. Though more granular than mainstream offensive baseball stats like batting average and home runs, those numbers similarly remain a measurement of results, not process.

Now, a dozen major league clubs and several training complexes, such as Driveline Baseball in suburban Seattle, are turning to a wearable technology that got its start in golf to help learn about how each player moves, rather than just what happens to the ball. K-Motion produces a tracking vest that captures and quantifies the biomechanics of a swing.

“It’s been tremendous for us in getting an objective understanding of how our athletes are moving when they swing,” said Driveline’s director of hitting, Jason Ochart. “We’re used to using video, but video has limitations.”

This technology is not completely new but previously had been relegated to biomechanics labs. Such setups are not portable and are very expensive. Ochart said Driveline’s facility uses 15 cameras with a collective cost well into the six figures. (Driveline’s tech helps with cutting-edge pitch design.) Tracking hitting in such an environment carries additional risk that pitching doesn’t. Namely, batted balls could go anywhere. Errant projectiles and expensive equipment make for a dangerous combination. “Kyle wouldn’t be too happy if a foul ball hit one,” Ochart said, referring to Driveline founder, Kyle Boddy.

The K-Motion vest can be used anywhere and can detail the speed and amount a player’s torso and pelvis bend as well as the rotation of their body at various segments of a swing. These metrics on a hitter’s posture and positioning can help identify and remedy mechanical flaws. The Seattle Mariners are a client of K-Motion, and they hired a coach as a specialist to work with their minor league hitters with the device. Driveline can collect data off its hitters anywhere in the training center’s building.

“K-vest has allowed us to collect data off of a pitching machine, off of a live arm,” Ochart said. “It’s allowed us to get kinematic data on hitters when they’re basically in a game scenario.”

Driveline runs every new hitter through a standard assessment that includes K-Motion. The data is presented in real-time, which helps with quick adjustments. But the aggregation of that data has helped with a general understanding of mechanics and K-Motion’s biofeedback can change how athletes train.

“Initially we just used it for collection [of data] because we didn’t know what a good swing was, right?” Ochart said. “We had ideas, but as you know, at Driveline, we’re very particular about what we speak as true and what isn’t.”

With more than 70 pro hitters in its database, Driveline has been able to build a profile of an ideal swing, or something close to it. Ochart and his team can compare the sequencing of a hitter’s movements with what’s been shown to work. From there, they can tailor a hitter’s workout and drills accordingly.

“What the K-Vest has done is it’s really shown the importance of the upper extremities,” Ochart said. “In hitting, we talk about the engine a lot—we talk about the pelvis and torso, which clearly are important—but I’m finding that the best hitters in the world are really good at transferring that energy with their arms and wrists. They’re really able to accelerate up through the chain.”

Discussing the function of the arms and hands in the swing while looking at the K-Vest data from a swing of a 19 year old minor leaguer and top prospect pic.twitter.com/XvN1mG5f7h — Jason Ochart (@JasonOchart) November 1, 2018

Driveline has tracked numerous high school and college hitters, as well, and has seen clear patterns of stratification. Some youth hitters, Ochart said, are unable to generate what hitting coaches call a “whip”—an acceleration of movement with the hands to create more power. For those players, the speed of their swing is basically just the speed of their torso rotation.

Sometimes the issue is physical, not mechanical. K-Motion CEO Michael Chu, for instance, had a history of right knee injuries from playing volleyball. In using the device to study his own biomechanics, he discovered an issue in the way he jumped and landed. The technology’s application is broad. Chu has worn the product to monitor his form doing squats. Sprinters and skaters have used the vest to determine their efficiency of movements. Recently, some Austrian ski jumpers have started wearing it, too.

But baseball is the hottest market. Chu said he went from two MLB clients to 12 very quickly, and amateur hitters are buying in. While physical talent will always be a limiting factor, tinkering even a small amount with a professional’s swing can pay huge dividends.

“In the game of baseball, if you can change someone’s position of their setup so they can deliver the barrel better,” Ochart said, “it can be a career-changing adjustment.”