GLENDALE, Ariz. -- With the late afternoon sun beating down, Mountain Ridge High School's varsity quarterback lined up under center to run plays. Receivers sharpened their routes and cornerbacks honed their man-to-man coverage.
About 200 feet away, another position unit worked on footwork and agility by running quickly between step-over dummies.
The team's white pads and helmets sat to the side the entire time.
"Do we go pads now?" a coach yelled out from the middle of the practice field.
"We can't until 6," head coach Bobby Green yelled back.
In an effort to further reduce concussions and other brain injuries, the Arizona Interscholastic Association implemented a rule this fall that allows teams to only use one-third of practice time for live contact in the regular season. During the preseason, live contact is allowed for half of practice.
The rule is the first of its kind to limit contact in high school practice, according to the National Federation of High School Associations.
"I think it's real important," Green said. "It's good to monitor how much contact is in practice to limit some of the concussions."
The contact limitation follows a 2011 state law that requires a high school athlete to be removed from play if the student is at all suspected of sustaining a concussion and then given written clearance from a medical professional to return. The AIA then partnered with Barrow Neurological Institute to create BrainBook, an interactive online education also required by the law for all high school athletes, and Brain Ball, a smartphone-based game that expands on those lessons.
After a Mountain Ridge player sustained a concussion in the season opener, coaches preached concussion awareness while the Mountain Lions ran contact-free drills.
As linemen practiced hand-fighting pop-up bags on the way to sacking an imaginary quarterback, assistant coach Kip Thomas made sure they were using the correct tackling technique to prevent a high hit to the head.
"You gotta stay low," Thomas told the players. "I should not see anybody's head behind this bag."
According to the AIA, a 2012 study of 20 high school sports reported that one-third of concussions occur during practice. Another study showed that injuries didn't increase during games when contact was limited in practice.
Green said he's seen more concussions occur in games than practice but doesn't believe that the lack of contact in practice will lead to any issues.
"It hinders practice in the sense of trying to get as much live contact in," Green said. "Now with that rule, I don't think it'll make them less prepared (to take hits)."
The AIA declined an interview request, but associate executive director Chuck Schmidt said at a news conference in late August the rule aimed to address renewed awareness of football's risks.
"As the research would suggest, the limitations on practice contact does not have an impact on their ability to tackle or play the game of football," Schmidt said.
Bryce Nalepa, athletic-training coordinator at the Banner Concussion Center, said the rule simply limits the amount of exposure players have to sustaining a concussion.
"High schools are really where you want to start this type of foundation," Nalepa said.
Nalepa said that experts realize, though, that concussions can't be prevented altogether in a sport in which contact is so ingrained.
"A lot of times it's when someone doesn't see the hit coming," Nalepa said. "There's no blueprint for concussions."
Because concussions won't be eliminated entirely, Green said that ensuring players can recognize concussion symptoms goes a long way in treating them.
"We're educating the kids about it," Green said. "They're more in tune with what's going on with their own bodies."
Bob Colgate, director of sports and sports medicine for the National Federation of High School Associations, said that the regulation is a step in the right direction, but he doesn't see it as groundbreaking.
"It's something that comes with the times," Colgate said.
Other states will now be watching Arizona closely to see how the rule plays out, but each will approach it differently, he added.
Green said he expects other states to follow Arizona's lead.
"If that's something that's going to allow them to be in more of a safe environment, then I think that it's something that's going to be nationwide," Green said. "It's something that's here to stay."
Nalepa with the Banner Concussion Center said it's reasonable to assume that concussions will limit student participation in high school football.
When former NFL players aren't allowing their own children to play with concussion concerns, there's going to be backlash among all levels of the sport, he added.
"It's becoming a real fear out there," Nalepa said. "Sports that have contact are on the threshold of becoming extinct."
Now that the dangers of concussions in football are out there, more and more parents will hold their children out of playing, Green said.
"We're taking the steps necessary to protect," Green said. "I still think the game is safe."
• A new Arizona Interscholastic Association rule limits how much of a high school football practice may involve contact drills.
• A 2011 state law requires that high school athletes be removed from play if even suspected of a concussion and kept off the field until given written clearance to return.
• That law also requires concussion education for all high school athletes, which AIA created in the form of an interactive online course called BrainBook.
• Free baseline cognitive testing, known as ImPACT, is provided for all AIA-member schools that don't offer it on their own.