In a move that could potentially decide wins and losses, Major League Baseball is allowing players to wear continuous biometric monitors during games.

Made by Boston-based Whoop, the wrist-worn monitors will measure heart rate and fatigue levels during in-game competition among the major North American pro sports leagues. Players can choose if they want to wear the device or not.

An MLB spokesman confirmed Monday's news, but didn't provide additional comment. Baseball has a deal with the Major League Baseball Players Association allowing the use of some wearable devices both in- and out- of games dating back to last season. The players' association didn't respond to requests for comment.

The decision to allow big-league baseball players to wear Whoop monitors during games is the latest step for integrating technology into the national pastime. Last season, MLB allowed the Motus Baseball sleeve, which tracks throwing, and the Zephyr BioHarness, a chest strap that monitors heart and breathing rates, to be used in actual games.

Whoop's deal comes about three months after the company released a comprehensive study in cooperation with MLB that showed a correlation between monitoring recovery and injury and quality of hitting and pitching. The study was conducted using 230 minor league players from nine major league teams.

Whoop CEO Will Ahmed said in a blog post Monday that MLB clubs can now use a "Day Strain" metric to determine whether a pitcher is tired, instead of just tracking of how many pitches he's thrown during a game.

"Clubs could find out that player X is no longer effective when his 'Day Strain' hits a certain number, regardless of whether he's thrown 50 pitches or 100 pitches to that point," he said.

Among the teams that participated in Whoop's study last season was the Philadelphia Phillies. General Manager Matt Klentak said during baseball's winter meetings in December that he's looking beyond analytics to improve his club that lost 91 out of 162 games in 2016.

"It's about objectivity and making better decisions. It's not just about batting average and earned run average and on-field performance," he said. "It's whatever data we can acquire that helps us make better decisions."

Whoop is also popular among NBA players. Last week, Los Angeles Clippers all-star DeAndre Jordan admitted to hiding his Whoop tracker under a wristband during a recent game. Last year, the NBA banned then-Cleveland Cavaliers guard Matthew Dellavedova from wearing his Whoop tracker after he did for 15 games. The league allows teams to use wearable tech in practices but not in games.

Last year, baseball minor leaguers involved with Whoop's study voluntarily wore a tracker which is similar to a wristwatch but without a screen, at all times except during games. The players' strain, recovery and sleep levels were analyzed as up to 100 megabytes of data was reported daily through a smartphone app. The data also gave recommendations for personalized programs.

Whoop's goal is to "unlock" human performance, Amhed said in his blog post.

"We believe that athletes and competitors alike deserve data to help them better understand their bodies," said Amhed. "This data, particularly recovery data -- will make for healthier athletes, longer careers. I know teams, athletes, and fans alike can benefit from that."

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