In the wake of a new study showing that head impacts among second-grade football players are sometimes as severe as those seen at the college level, the national president of Pop Warner said he will propose a rule that, for the first time, would limit the amount of contact allowed in practices.

Jon Butler, who heads the nation's oldest and largest youth football organization, told ESPN on Wednesday that his membership needs to take action to protect the safety of children and prevent attrition driven by parents who are increasingly concerned about concussion risks.

"I'd like to see contact drills limited to a third of all practice hours," said Butler, who plans to introduce the measure at a Pop Warner national meeting that starts Wednesday in Baltimore. "We allow six hours of practice a week, so that means two hours of contact drills -- that, or less."

Butler's move comes on the same day that a team of researchers at Virginia Tech and Wake Forest universities released the first-ever study that measures head impacts among youth football players. The study found that unlike in high school and college football, most of the severe hits in youth football occurred during practices.

The authors, led by Stefan M. Duma of the Center for Injury Biomechanics, called for the elimination of high-impact practice drills that do not replicate game situations, such as drills where players are asked to line up and run right at each other.

"Head impact exposure in youth football, particularly at higher severities, can be reduced through evaluating and restructuring practices," they wrote. "This can be achieved through teaching proper tackling techniques and minimizing drills that involve full contact; and instead, focusing on practicing fundamental skill sets needed in football at these young ages."

The sample size was small -- just seven players in a Virginia youth league between the ages of 7 and 8 -- but its findings will help shape the debate about safety measures, and for some, whether children should participate at all, in youth football, which is played by 3.5 million children younger than high school age. The average player in the study sustained 107 head impacts during the course of 9.4 practices and 4.7 games.

Most of those hits were modest in force, as measured by sensors installed in the padding of helmets. But some topped 80 g's, similar to "some of the more severe impacts that college players experience, even though the youth players have less body mass and play at slower speeds," the authors wrote. Boys of grade-school and middle-school age often lack the neck strength of teenagers, among other factors that can make them vulnerable to injury.

Chris Nowinski, co-founder of the Sports Legacy Institute, told ESPN that the Virginia Tech study provided "urgently needed data" on the dangers of youth football -- where, unlike in the NFL, college and high schools, there has been little research. The majority of the high-level impacts occurred during practices, which accounted for 29 of the 38 impacts above 40 g's.

"I am shocked to see that these children receive levels of brain trauma comparable to college football players," Nowinski said. "At one-third to one-fourth the mass of the average college player, it appears they deliver and receive nearly the same force to the brain on each hit."

He also noted: "The 107 hits (per) season average is likely below what most youth teams in America experience, as each player in this study averaged a total of only 14.1 games and practices combined. The finding that the majority of high level came in practice provides more evidence that football needs to follow the lead of the NFL and Ivy League and restrict hitting in practice."

Nowinski's co-director at the Sports Legacy Institute, Dr. Robert Cantu, sent shock waves through the youth football establishment when he recommended that children under 14 not play collision sports like football, ice hockey, soccer, and lacrosse until they are modified to eliminate head blows in routine practice and play.

Butler said some contact is necessary in youth practices, as, unlike NFL and college players, many children have not yet learned how to tackle and protect themselves. He also said that although his flag football division has seen robust growth in recent years, he does not believe many parents are ready to shift their children to that form of the sport when young.

"We've seen proposals to get rid of tackle football for kids," Butler said. "But I truly believe that if we went in that direction, 90 to 95 percent of our numbers would drop out of Pop Warner and find another way to play tackle football."

He said he hopes that the Pop Warner membership votes to pass a rule limiting contact by the end of its meeting Friday. Duma and Nowinski told ESPN that they support Butler's proposal.

As a follow-up, the Virginia Tech and Wake Forest researchers announced Wednesday the launch of a new study to measure and map the head impact exposure of youth football players for all age groups between 6 and 18. The study will consist of more than 240 helmets with special sensors on six different football teams in Virginia and North Carolina.

"The magnitude of forces in this population is eye-opening, as is the fact that there are many high contact/impact practices within this small sample of children," said Micky Collins, who runs the nation's largest concussion management clinics at the University of Pittsburgh Medical Center. "This is an excellent first step for studying youth football and biomechanical aspects of concussion, though further research is needed to better clarify these issues across a larger sample size and wider age range."

Tom Farrey is an ESPN correspondent and can be reached at tom.farrey@espn.com. He can also be followed on Twitter at @TomFarrey.