The Optimeye GPS monitor is about the size and shape of an old flip cellphone, only lighter.
In practices this offseason, select Green Bay Packers players have been wearing it on their backs, held by a sports bra-type pullover. While the players go through their drills, the Optimeye collects data 10 times per second to measure the speed, explosiveness and distance of their every move.
"You don't notice it," safety Morgan Burnett said last week. "That thing on your back is the last thing on your mind. You can't even tell you've got it on."
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Catapult Sports of Australia, which makes the Optimeye system, is one of several companies on the cutting edge of GPS and other technologies that are trying to make sports training more scientific and evidence based.
The GPS technology was developed in Australia in the early 2000s and has been mainstream in pro sports there for several years. It's also become heavily used in European soccer in recent years and is starting to take off in the United States.
Catapult works with about 400 high-level teams and sports organizations worldwide, including soccer clubs in the English Premier League, professional rugby and Australian rules football teams, at least six NBA teams, and 14 teams in the NFL. Some NFL teams have asked Catapult not to say they're clients, but among those using Catapult are the Packers, New York Giants, Atlanta Falcons and Dallas Cowboys.
Catapult and its competitors in GPS, such as another Australian company, GPSports, are part of a wider movement in sports science to develop wearable technology to monitor athletes. A start-up company in the U.S., MC10, is developing a patch called Biostamp that records heart rate, muscle activity and hydration. Another company, Athos, makes smart sports shirts and shorts that track muscle output, and Basis makes wristbands that monitor heart rate and sleep.
The Packers for now are using only a GPS-based system, which measures external load (i.e., the force and distance movements generate) but not internal load (the body response from the player making those movements). Along with the GPS, the Optimeye contains an accelerometer and gyroscope that when combined with software can measure a player's workload on movements in all directions and force of collisions with other players.
The data for each player is collected and available either in real time on handheld devices such as smartphones and tablets, or after practice. Teams in Australian rules football and rugby have years of data to guide them and use GPS to monitor players during practice and games; the Packers appear to be using it primarily to analyze post-practice and guide the workout plan the next day.
"We want to push players physically and mentally as far as we can," said Dr. Tim Gabbett, a sports scientist at Australian Catholic University in Brisbane and worldwide consultant for teams using GPS technology. "Take them to a bad place, so when they get put in a bad place in competition they've been there before, they know what to expect.
"But in season, we use GPS to make sure we don't overtrain the players. They typically have planned loads for a particular session, and the head coach is well aware of what that planned load is. You might only cover 4½ kilometers (in a practice), and he wants to get his skill work done, but he has to get it done in that constraint."
The GPS devices also can be synced with heart monitors so teams can compare how a player reacts to a workload. If he's more fatigued than usual during a given drill, he might be more susceptible to injury, and thus see his practice reps reduced or even eliminated the rest of the drill or day.
It appears the Packers are using only the GPS technology, not heart monitors. At least for now, heart monitors are difficult to work with in sports such as football because they're worn as a strap across the chest that's easily dislodged with the kind of contact that occurs on every play in practice.
Still, as the technology improves, it will be part of the future of sports technology, which will be twofold: The devices to measure activity will get smaller and more accurate, and they'll be combined to provide a complete picture of an athlete's conditioning, performance level and susceptibility to injury.
The GPS measures the external loads (how far, fast, and explosively an athlete moved in any direction), while other devices will measure biometrics (heart rate, respiration, perspiration, hydration, muscle activity, hormonal response and lactic-acid accumulation) that accompanied those movements.
"You're only limited by your imagination in the number of sport-specific movements you can measure and quantify," Gabbett said. "That's going to be the future. In the next few years, we'll not only measure the distance traveled but the demands of sport-specific movement. It could be a quarterback throwing the ball, how many times, how much intensity is in those throws.
"You actually start to measure load in a number of ways that are very specific to the individual and the playing position."
— email@example.com and follow him on Twitter @PeteDougherty.