Major League Baseball (MLB) has approved two wearable biometric devices for use during games, the organization told IEEE Spectrum this week. Players will be allowed to wear the Motus baseball sleeve, which tracks strain on pitching arms, and the movement-tracking Zephyr bioharness during the 2016 season says Mike Teevan, an MLB spokesperson. The organization had previously remained silent on the issue.
Meanwhile, the National Basketball Association (NBA) last week reprimanded a player for wearing the Whoop wristband, which, along with all wearables, is banned during NBA games. The contrasting league policies, along with some ambiguity about what exactly is allowed, has resulted in a rocky start for the niche market for wearables tailored for elite athletes.
Outside of official games, the use of wearable biometric devices in professional sports has exploded in the last couple of years. Teams pay thousands of dollars for high tech gadgets that track physiological measurements so players can optimize performance and avoid injury. These sensors offer far more detailed and accurate data than consumer-oriented fitness trackers like Fitbit, and tend to be backed with analytics tailored for the athletic elite. Professional athletes have been spotted wearing biometric trackers during practice, warm-ups, around town, and even in commercial spots. (Check out LeBron James’ wrist in a recent Kia commercial).
But for the most part, professional sports leagues have held back on approving the devices for in-game use. In addition to the NBA, the National Football League (NFL) and the National Hockey League (NHL) have each drawn a clear line in the sand: no wearables during games.
That doesn’t mean players won’t wear them anyway. And it might be hard to police since many of the sensors are are easy to hide. Catapult Sports’ OptimEye sits over the upper back in a compression garment worn under the shirt. Some postage stamp-sized sensors can be affixed to the skin like temporary tattoos.
Cleveland Cavaliers point guard Matthew Dellavedova in March got caught wearing the Whoop wristband, which tracks heart rate, body temperature and movement. The device is clearly visible—it’s a wide black band worn around the wrist. Yet Dellavedova wore it for 15 games before the NBA noticed. “Wearable devices are not permitted to be worn during games and yes, we asked Matthew to stop wearing them when we noticed he was,” says Tim Frank, a spokesman for the NBA. Neither the Cavaliers nor Dellavedova were fined for the infraction.
High-tech wearables are so new and potentially disruptive, sports leagues may have good reason to put restrictions on them for now. There are several issues to consider. The devices could give players who wear them an unfair advantage, especially if they provide real-time feedback during games. There’s also a safety factor, like getting hit in the face by a hunk of hard plastic. And some players are concerned about privacy or that the data from the devices could be used against them. Player unions are aware of the concerns, and the issue will likely be a point of negotiation for many of them.
Major League Baseball is tiptoeing into in-game wearables—but quietly, and a bit ambiguously. Last year, for the first time, the league allowed players to don the Motus baseball sleeve by Motus Global in Massapequa, N.Y. The device tracks strain on a pitchers’ elbow, and aims to improve pitching mechanics in order to prevent the epidemic of injuries that has led to a seemingly endless procession of pitchers having the reconstructive procedure known as Tommy John surgery.
But the League’s decision wasn’t entirely clear to Motus. “We were granted provisional approval for the 2015 season but there was confusion as to what that meant at the MLB level,” says Motus’ chief technology officer Ben Hansen. “There was use at the [minor league] level [in 2015]. The League’s process this year is much more clearly defined and we anticipate strong adoption at all levels,” he says.
MLB approved the device again for use in the season that just began this month, along with a new one to the game: the Zephyr bioharness by Annapolis, M.D.–based Medtronic. That device straps to the chest and measures heart rate, respiration, peak acceleration, speed, distance, and GPS location, among other metrics.
Teams are not allowed to access the data from either the Motus or Zephyr devices in real time; they must download it after the game, says MLB’s Teevan. Electronic equipment such as tablets have, in the past, been prohibited on the field or in the dugout during games. But that changed too this spring when MLB announced that it had partnered with Apple to equip every team with iPad Pros. Those devices will not have Bluetooth capability enabled, according to a person close to the matter who asked to remain anonymous.
MLB asked the makers of the Zephyr and Motus devices to keep quiet about the in-game approval of their devices. Even after the Associated Press last week reported, based on an anonymous source, that the MLB had given a green light to the two devices, MLB asked Medtronic not to discuss the matter, says Mark Santini, a senior global product manager at the company.
Why so hush-hush? It’s unclear whether it has anything to do with the privacy, safety, and fairness issues surrounding wearables. Professional sports leagues, including MLB, have been known to keep close tabs on companies that make products for their teams. They often ask companies not to use the league’s name to promote commercial products.
IEEE Spectrum was able to get confirmation of the approval of Zephyr and Motus as equipment suppliers directly from MLB after approaching the league from a couple of avenues.
Motus Global, for its part, is busy launching second-generation versions of its monitoring sleeve—one for youth players and the other for professionals. The latter, a souped-up network of five sensors called Motus Pro, can track more than 40 pitching and batting metrics and full body movements. The company is continuing to collect data from professional players in an effort to identify trends in workload changes that can lead to injury. “We’re still crunching numbers,” says Motus’ Hansen. “But we’re starting to see some trends.” MLB has yet to approve the five-sensor Motus Pro for in-game use.
Emily Waltz is a features editor at Spectrum covering power and energy. Prior to joining the staff in January 2024, Emily spent 18 years as a freelance journalist covering biotechnology, primarily for the Nature research journals and Spectrum. Her work has also appeared in Scientific American, Discover, Outside, and the New York Times. Emily has a master's degree from Columbia University Graduate School of Journalism and an undergraduate degree from Vanderbilt University. With every word she writes, Emily strives to say something true and useful. She posts on Twitter/X @EmWaltz and her portfolio can be found on her website.