The issue of contact practice limits has generated significant contoversy. Researchers at the University of Pittsburgh Medical Center suggested, based on data showing that youth football players sustained concussions at about the same rate in practice and overall as high school and college athletes but suffered concussions in games at a rate 3 to 4 times higher than older players during games,  that Pop Warner's limits on full-contact practice might be counterproductive.
Indeed, expanding on the study's main finding, Michael Collins, a study co-author and executive and clinical director of the UPMC concussion program, went even further; in an interview with the Pittsburgh Post-Gazette, Collins went so far as to say that such limits were "short-sighted, because practice is an opportunity to teach proper technique, for kids to learn how to do this the right way."
Of the 18,000 concussion patients who visit the UPMC clinic every year, Collins said, "the worst cases I see are kids who on August 15 ... decide to go out for football without ever learning the sport. The don't know how to tackle or play, they get lit up."
No surprisingly, pushback to the study and Collins' remarks from Pop Warner was immediate. Julian Bailes, M.D., co-director of the NorthShore University HealthSystem Neurological Institute in Chicago and chair of Pop Warner youth football's medical advisory board, told USA Today that the study's suggestion that Pop Warner had gotten it wrong when it moved in 2012 to limit contact in practices was "erroneous" and sent a "bad message" to players, coaches, and parents.
Bailes told the Post-Gazette, "Those who played and coached the game know it's very possible to still teach technique without going head-to-head full contact. If they're implying you need head-to-head full contact to learn proper technique, I disagree and think they are erroneous in that conclusion."
Indeed, Bailes went so far as to tell USA Today that "to think more hitting your brain is good for you or doesn't make any difference if you do it in practice is asinine."
First, do no harm
Also expressing reservations about the UPMC study's main conclusion was Bennett Omalu, MD, one of the leading forensic pathologists in the field, well-known for his post-mortem research on head trauma. "The very basic medical principle, research or no research, is 'Do no harm,'" Dr. Omalu told the Post-Gazette.
"Anybody who tells me that willfully exposing the brains of children to repeated impact is something good, I would humbly disagree with that person. I am not an advocate for the idea that football should be banned or not played -- I am not that extreme. I stand with Pop Warner, and I stand with caution. Limit the exposure of children from repeated blows to the head in whatever activity they do."
While not surprised by the study's finding that the vast majority of concussions occur in games, Jon Butler, executive director of Pop Warner, was not expecting the UPMC researchers' suggestion that not enough contact in practice may be detrimental. "It surprises me that they say limiting contact in practice may have a reverse effect, essentially," Butler told USA Today, noting that much of the teaching of proper tackling technique is done at slow speeds without full contact.
Kontos was quick to tell USA Today that Bailes was misreading what the study said. "We don't want more head-to-head contact. What we want is more contact practices where we teach proper technique to avoid head-to-head collisions in games. And, if we don't have good practices to teach that, we're sending kids out unprepared to make those tackles."
To be fair, Kontos and his co-authors do make a point of noting in their study that "we know little about the potential for long-term effects from repetitive exposures to subconcussive impacts that might occur in practices and games. As such, we cannot discount the potential effects of reducing practice exposures on effects related to repetitive subconcussive impacts."
Limits don't increase risk, new study says
A subsequent study by researchers at Wake Forest Baptist Medical Center and Virginia Tech seems to support the positions staked out by Bailes, Omalu and Butler, suggesting that less contact during practice could mean a lot less exposure to head injuries among young football players and the kind of repetitive subconcussive blows that some researchers suggest can lead to long-term brain injury, without increasing exposure to higher impact hits during games. 
The new study involved one team that, while not affiliated with Pop Warner, chose to follow its new practice rules, and two others that did not. Significantly, the data showed that reducing the number of head hits in practice did not, as the UPMC predicted, lead to higher force impacts during games.
"The concern is if we don't teach kids how to hit in practice, they're going to get blown away in the games," said Stefan Duma of the School of Biomedical Engineering and Sciences and one of the co-authors of the study, in an interview with The New York Times. "This shows you can dramatically cut the amount of exposure in practice and have no more exposure during the games."