In the past tracking the performance of athletes was a bit more complicated and harder than it is today. This is because today wearables have become a lot more accurate, a lot more accessible, and also a lot more affordable, which means that outfitting a sports team with a fitness tracker would be financially feasible.
That being said in a report from ESPN, it seems that the Major League Baseball has given the greenlight for a new wearable that can be used by players during a game. This makes it the second such device that the League has approved. This device comes in the form of a tracker made by a company called Whoop.
This tracker could be seen as a more advanced version of fitness trackers because not only does it track your heart rate, but it can also track things like heart rate variability, ambient temperature, motion, and sleep data. This data can be stored on the device for up to 3 days, meaning that coaches can monitor the vitals of their players heading up to a game.