Since taking over as Green Bay Packers coach in 2006, Mike McCarthy traditionally started practices with a jog-through, usually ranging from 20 to 40 minutes.
The slow-paced period, with the offense at one end of the field and the defense at the other, is a scripted rehearsal of particular offensive play calls against particular defensive play calls. The players see the alignments, practice their audibles and checks, then carry out assignments at a jog.
This spring, though, McCarthy moved jog-through to the final period of practice. While that might seem relatively insignificant, McCarthy doesn't change his team's work schedule without good reason, and his reason here is obvious: Injury prevention.
According to an injury-rating system devised by FootballOutsiders.com, the Packers have ranked among the three most-injured teams in the NFL in three of the past four years. This is one of McCarthy's responses, particularly to the seeming epidemic of noncontact, soft-tissue injuries.
"I've always felt since the first day I came here that scheduling and how you train a football team is the most important part of the head coach's job," McCarthy said last week about his attempts to reduce injuries. "That's another competitive arena you're in. How you train your team compared to your opponent can give you an edge."
To that end, McCarthy won't discuss in any detail the whys and hows of changes in his training and practice regimen. But it's clear he based the jog-through move on research from the fast-growing field of sports science, which includes work by his strength and conditioning coach, Mark Lovat, and the hiring this offseason of the Australian GPS technology firm Catapult Sports.
"You have to be open to new ideas and different ways," McCarthy said. "We have a very talented — Mark Lovat, I'll put him up against anybody in this business, not only now with his experience but growing up in the business and knowing the old way. Continuing education goes on here all the time. Our support staff is very experienced and well-connected in sports science throughout all sports, not just football."
The Packers' latest addition in sports science is Catapult, which introduced GPS technology for monitoring athletes in the early 2000s that now is mainstream in professional sports in Australia. The Packers appear to have used a GPS system for the first time last year but switched to Catapult this spring.
In offseason practices, select players have been wearing a GPS device that includes an accelerometer and gyroscope. Combined with software, it measures a player's movement in practice, including his speed at any given time, distance covered, explosive movements in any direction and the force of physical contact.
Australian sports scientists have been studying GPS technology for more than a decade and remain on the cutting edge — their high-level sports teams use it more extensively than anyone in Europe or the United States. In Australian rules football, for instance, every player on every team wears the device in all practices and games, which provides each team with an enormous amount of data about its players' workloads.
"It takes the art out of training," said Dr. Tim Gabbett, an associate professor of exercise science at Australian Catholic University in Brisbane who has published numerous papers on GPS-based athlete monitoring and works as a consultant to teams in various sports.
"You can actually put a lot more science behind your training. I still think it's never going to replace good strength and conditioning coaching, it's never going to replace good coaching. It's there to complement your really good coaching."
The challenge for the Packers, and all coaches in all sports, is to condition players' bodies and minds for peak performance while not significantly increasing injury risk by overtraining.
GPS devices are the most advanced tool for trying to determine that line, though they provide so much information that the key is discerning what's relevant in the noise. In Australia, where the three biggest running-based team sports are Australian football, rugby and soccer, the devices have significantly changed the way teams train over the past decade.
"Once you've got a few years of data built up, then you can set pretty good training loads without having those spikes in injury risks," said Rich Johnston, a conditioning coach for the professional Australian Rugby League team Norths Devils and sports scientist at Australian Catholic University. "You can know whether they're doing too much or too little and tailor it to the individual."
Avoiding data 'pollution'
The Packers appear to be easing into use of the devices rather than deploying them in the targeted, individualized manner of Australian teams.
Interviews with players in the locker room last week suggest that all or almost all of the team's receivers, running backs and defensive backs wear the devices in practice. They do the most running. Only one of three offensive linemen asked said he wears one, and players at other positions either weren't available or said they hadn't worn one.
McCarthy appears concerned about overloading his coaching staff with information and seems to be monitoring the general workload of position groups rather than basing an individual's daily workload on his data.
"It's always great to have as much information as you can," McCarthy said. "But the longer I do this job, there's more (information) pollution out there. That's where you have to stay practical."
Still, it's not hard to envision the Packers and other NFL teams expanding GPS use in the next few years. Florida State football coach Jimbo Fisher, for instance, has said using GPS technology helped his national championship-winning team reduce soft-tissue injuries (muscle pulls and tears) by 88 percent since he started using it two years ago. And published studies from sports such as Australian rugby strongly suggest there's much to gain in injury prevention with GPS.
For instance, in 2010, Gabbett finished a four-year study on a professional rugby team using GPS data that showed players who trained significantly over a certain threshold — the thresholds were different for preseason, early season and late season — were 70 times more likely to sustain a soft-tissue, noncontact injury than players who stayed near or below that workload.
"If teams like Green Bay are getting a lot of soft-tissue injuries, this kind of stuff can actually be used to minimize the injuries and make sure you get your best players available," Gabbett said.
The extensive use of GPS technology in Australia has changed significantly the way their teams train and deploy players in games over the past decade.
In Australian rules football, which features long sprints and extensive contact on a large field, training before GPS technology often consisted of long-distance running. But after measuring game performance with the devices, teams realized that while players covered a lot of ground in a match, their mileage came via relatively short bursts that ranged from moderate to very high intensity. So they've trained more for speed endurance rather than endurance.
"A player might have to do 10 high-intensity efforts within 5 minutes, and during this period they might cover almost a kilometer of running," said Michael Rennie, the conditioning coach for the Sydney Swans of the Australian Football League and a Ph.D. candidate at University of Technology, Sydney.
"What we do is train them above and beyond the worst-case scenario they're going to experience in a game, and if that happens within a game, they've done it 1,001 times already and they're prepared. Therefore, your injury risk is much, much less as well, because they're physiologically and mechanically prepared."
NFL structure not optimal
GPS research from Australia also strongly suggests that while players in contact sports can withstand high workloads in the preseason, they need to get to capacity gradually. Anything more than a 10 percent bump in workload a week significantly increases injury risk. That research suggests the NFL's collectively bargained offseason training schedule is far from optimal for possible injury prevention.
Australian professional rugby, for example, allows for a gradual weekly increase to get ready for games. Preseason training lasts 12 to 14 weeks, with only a one- or two-week break for Christmas in the middle, and then rolls immediately into the six-month regular season.
The NFL's offseason training program is more fragmented. It starts in late April, runs for nine weeks, and is followed by a five-week break before the start of training camp. Training camp then is short (five weeks), and most of the highest-intensity practices are in the first two weeks.
That means NFL players don't get team-structured work to gradually build up to the most demanding practices. Many hire personal trainers for their pre-camp training. But unless they're working at high levels, they might be more susceptible to injuries early in camp.
"High training loads are not the enemy, we need them to prepare players for the season," said Johnston, the rugby conditioning coach. "But we do need to program these loads in the right way, so there are no massive spikes in training. You might get (spikes) with the (NFL's) current model, where players perform their own training before going into a big camp."
The NFL doesn't allow players to wear GPS in games, but the Australian Football League does. In that league, teams use GPS for substitution patterns.
Some players have caps on their workload for a game, so they're rested as they get nearer the cap, and usually for only about 3 minutes rather than for long stretches, which is another lesson about recovery from monitoring devices. Then when a player reaches his cap, he's pulled for good.
"We know after a certain period of time of high intensity work, your performance goes down," Rennie said. "We try to treat that rotation strategically based on who needs rest."
Among the other insights from studies of GPS technology, one goes back to McCarthy's decision to move jog-throughs.
For years, coaches in team sports assumed that low-impact work such as walk-throughs and jog-throughs in football and rugby, shoot-arounds in basketball and even pregame warm-ups in soccer took minimal physical toll on their players. But in the past few years, studies using GPS technology in conjunction with heart monitors and other measures of athletes' efforts showed that kind of work was far more taxing than assumed.
Moving the long jog-throughs to the end of practice means the players are measurably less fatigued for the full-speed work that makes up the majority of practice. The players still expend effort doing the jog-through at the end of the workout, but the low intensity level should leave them less susceptible to injury.
"Everyone's going to be training much more objectively and much more scientifically as we go forward," Johnston said. "I know everyone sees Australia as the front-runner (in GPS technology), but with the resources you have over (in the United States), the sky's the limit."
— firstname.lastname@example.org and follow him on Twitter @PeteDougherty.