It's one of the features of technology being used by about 30 college football teams and 15 NFL teams to monitor the movements and physical output of players during conditioning, practices and games.
The Australia-based company Catapult developed the system about eight years ago. Rugby and soccer teams were among the first to use it. Football teams in the United States began signing on with Catapult three years ago, and several hockey and basketball teams have followed.
"You build a portfolio of data on each player so over a period of time you can tell when they're wearing down, do they need an extra rest, do they need a day off, all those things," Tennessee coach Butch Jones said. "The most important thing is what you do throughout the week to get them ready to perform at their peak, at their optimal level, come game day."
At Nebraska, the top 50 football players slip a monitor weighing about 3 ounces into a pouch in the back of the tight-fit shirts they wear under their shoulder pads. Head strength coach James Dobson said it's too expensive to track all of the Huskers' 130 players. As it is, Nebraska will pay Catapult more than $363,000 over three years to rent equipment.
Each monitor includes a GPS device and other sensors that measure hundreds of variables per second, many of them hard to pronounce.
Some of the basic metrics: how far and fast did the player travel during a practice or game, his rate of acceleration, how many times he went right vs. left and whether he moved faster when he went one way or the other. The monitor is so sensitive that it can detect even a slight change in a player's gait, which can be a sign of fatigue or injury.
