Wired up: Digital devices the rage in baseball

Yankees reliever Dellin Betances wears a sleeve around his elbow to measure stress on a ligament.

Chris Coghlan spent spring training with the Phillies using a wrist band to check his sleep and recovery.

In 21st-century baseball, digital devices monitor heart rates, skin temperature — they even track fielder's movements, all part of the exponential data explosion used to determine batting orders, pitching changes and defensive shifts.

Major League Baseball's playing rules committee and the players' association approved four wearable technology devices for use during games this year, double the total of last season.

The WHOOP heart monitor and Catapult GPS tracker were added to the Motus Sleeve and Zephyr heart monitor.

Three additional devices have been approved for on-field use during pre-game practice: electronic bat sensors produced by Zepp Labs, Blast Motion and Diamond Kinetics.

Catapult's devices sit between the shoulder blades in a compression shirt and are used by Premier League champion Leicester and hundreds of other clubs in soccer, the NFL and cricket.

"Imagine being able to know throughout the course of a game or a pitching session or whatever, how does your intensity change, and maybe how does it change per throw, on a fastball vs. a curve vs. a changeup?" Catapult president Brian Kopp said.