Should gamblers see athletes’ heart rates during games?

Nix CEO Meridith Unger (right) heads a company that makes devices to analyze sweat for signs of dehydration.Suzanne Kreiter/Globe staff/Globe staff

Imagine you’re watching a football game. The kicker’s about to attempt a field goal. You check your sports-betting app, which tells you how fast his pulse is racing. Looks like he’s nervous — so you bet $5 he’ll miss.

As hockey players line up for a mid-game face-off, your smartphone buzzes with a proposition: Predict who will score the next goal, and win a prize. For a small fee, you can see real-time information about the hydration and muscle fatigue of each skater.

As Massachusetts lawmakers consider whether to legalize sports betting, professional athletes fear that their biometric data, increasingly collected and analyzed in training, could become a commodity in this new form of gambling

Unions for professional basketball, baseball, football, hockey, and soccer players say any sports-betting legislation should prohibit the commercial use of such data without player consent.

“That’s a person’s personal health information,” David Foster, an attorney with the National Basketball Players Association, told state lawmakers at a recent hearing. “That has no business in sports. It certainly has no business being bet on.”

Professional sports leagues say they have no plans to make biometric data available for sports betting, and that any future disputes about that issue could be handled in contract negotiations. Collective-bargaining agreements in the major sports leagues limit the use of wearable sensors in games, and some expressly prohibit commercial use of data from them without player permission.

But players unions want those protections enshrined in law. They’re concerned that leagues will see in-game sports betting as an increasingly attractive option to keep fans interested amid the ever-increasing chorus of smartphone distractions — and real-time information about the players’ bodies could make the experience more exciting.

The use of biometric data from wearable health devices is not covered by health privacy laws such as the federal Health Insurance Portability and Accountability Act, which means patients and employees have few protections.

Already, many fans know more about popular athletes’ bodies than they do their own — just ask a rabid Boston sports fan about David Price’s elbow, Tom Brady’s shoulder, or Zdeno Chara’s mouth. The disclosure of such information is usually a product of agreements and league rules that allow the sharing of injury information for competitive reasons.

Players are already wary about the biometric data collected in training being used against them in determining playing time or individual compensation. And some say that compelling players to publicize their vital signs or other real-time data for gambling would be a bridge too far.

“You increasingly go down a path of dehumanizing people if you go in that direction,” said Colin J. Zick, an attorney who leads the privacy and data security practice at Foley Hoag LLP.

Red Sox reliever Ryan Brasier said he does not think his fellow athletes would agree to such a program.

“I can’t imagine that’s something any player or team would want to be involved in,” he said in a brief interview.

It isn’t clear yet whether sports gambling products will seek to incorporate athletes’ health data, including information from wearable monitors. Gambling companies have so far stayed out of the public debate. DraftKings, a Boston daily fantasy sports company that is moving into sports betting, says it does not use biometric information in any of its products.

Bryan Seeley, who oversees security and investigations at Major League Baseball, told the Legislature’s Joint Committee on Economic Development and Emerging Technologies last week that the league has no intention of monetizing biometric data.

But he said Major League Baseball is concerned about proposals to legally prohibit the practice that go too far, and that could potentially cover data the leagues already collect about a player’s on-field performance — such as the result of an at-bat. Leagues, hungry for a cut of sports-betting revenues, want lawmakers to require bookmakers to use the official data compiled during games to settle bets.

Still, some in the industry believe some kind of biometric data will soon be available to people making live bets — perhaps within two to four years. Fitness-tracking technology is a rapidly growing business, with Fitbit and many other products guiding people’s personal health decisions across the nation. And the mores around gambling in sports are changing rapidly.

“Sports betting is pushing the envelope because it’s the biggest moneymaker, and it is one of the biggest ways, if not the biggest way, to engage fans in a game in real time,” said Kristy Gale, an Arizona attorney who focuses on sports and technology.

Pro athletes are already using some wearable technology as a way to provide fans with more information about what’s happening on the field. Since 2014, National Football League players have worn chips in their shoulder pads that collect data on their every in-game move. But commercially available sensors are capable of much more.

In Boston alone, several promising startups make products that can provide detailed information about athletes’ health, endurance, and performance.

Whoop, whose devices track users’ sleep and heart rate to measure recovery during training, signed a deal in 2017 with the NFL players union to provide an optional program to help athletes measure their training and recovery, and potentially find ways to make money from the data.

Humon makes a sensor that tracks how an athlete’s muscles are using oxygen. And Nix makes devices that can analyze sweat for signs of dehydration.

Meridith Unger, chief executive of Nix, said its technology was designed to help athletes learn how to work out safely and replace the fluids they were losing, not for betting purposes.

But she said Nix could provide data to viewers during a game, if leagues and players chose to use it that way. She said information on players’ hydration could provide “a sense of their relative fitness, or how much gas they have in the tank.”

Alessandro Babini, chief executive of Humon, said the commercialization of health data could be profitable but might make athletes feel uncomfortable using the products for training.

“We’re committed to creating a safe environment to athletes,” he said. “So when you sign into Humon, you’re not thinking, ‘Am I risking my data right now?’ ”

Debate about the use and ownership of biometric data was not a major issue in the first handful of states that legalized sports betting following a US Supreme Court decision last year that allowed the practice to expand beyond Nevada.

But the issue has gained prominence in recent months, pitting leagues and unions against each other in states that are considering sports betting — including Massachusetts and Illinois.

“When we’re formulating these laws, we have to think about today, but we also have to think about tomorrow,” said state Senator Eric P. Lesser, a Longmeadow Democrat and cochairman of the committee weighing whether to legalize sports betting here. “In a field like bioinformatics, you could easily think of a whole host of things that sound like science fiction, but very soon could become real life.”