J. Cournoyer, C. Karton, D. Koncan, M.D. Gilchrist, R.C. Cantu, and T.B. Hoshizaki.
How was this study done?
This study involved three stages of analysis: video analysis, laboratory reconstructions, and finite element modeling of head impacts from youth football games.
Video
Sixty football games were videotaped and were divided into two categories for ages 5 to 9 and 9 to 14-year-olds. There were 30 teams in each age group.
Head impacts were documented for 7 players on the team. The players were one quarterback, one running back, one wide receiver, one offensive lineman, one defensive lineman, one linebacker, and one defensive back.
For each verified head impact that was observed on the video, the researchers documented where the impact occurred on the head, and how it occurred, such as head-to-head or head-to-ground. The researchers then visually classified the velocity of the impact from very low to high.
Laboratory Reconstructions
Following the video analysis of the head impacts, the researchers simulated the impact scenario in the laboratory.
For these simulations they chose the head-to-head, head-to-ground, and head-to-shoulder impacts as these made up over 85% of the impacts seen on the videos. They used the small-sized NOCSAE headform for both age groups, fitted with a youth-sized football helmet.
Head-to-ground impacts were simulated using the free-fall drop test and head-to-head and head-to-shoulder simulations were completed using a pendulum test.
Finite Element Modeling (FEM)
The third component of the study involved using finite element modeling, which is a computer derived model of the brain that allows the researcher to enter an impact magnitude (from the laboratory reconstructions) into the model to determine peak Maximum Principal Strain. MPS is used to classify the severity of a head impact.
What were the results of the study?
In the group of 5 to 9-year-olds, the researchers recorded 590 head impacts in 30 games. In the group of 9 to 14-year-olds, researchers verified 805 head impacts. This difference in the number of impacts between groups is statistically insignificant. Statistically insignificant means that the difference could have happened by random chance and is not a real effect of what’s being studied.
In both age groups, most impacts were a result of head-to-head contact, and the next highest number were head-to-ground impacts.
Significance of Low MPS Values
The majority of impacts in both age groups had low MPS values. While impacts in this category may not be linked to diagnosed concussions, they are important to note because they are linked to injuries that lead to changes in brain structures and cognitive impairments that may not show symptoms.
Significance of Medium MPS Values
More impacts in the moderate-range category occurred in the younger group than in the older group. Moderate-range MPS level impacts have been associated with concussions. This higher number of moderate-range impacts appears to be due to the relative inability of younger kids to control the the motion of their heads during an impact event. Further, because the added weight of a helmet adds to this problem, the researchers concluded that younger athletes may benefit from a smaller and lighter helmet.
Impacts by Player Position
In both age categories most of the head impacts occurred to running backs, followed by defensive line players, and then linebackers. Impact events were similar for both age groups as well. Most impacts were a result of head-to-head followed in number by head-to-ground.
Change in Testing Criteria to Capture Lower Magnitude Impacts
Laboratory reconstructions of the impacts showed that measurements of peak linear and rotational accelerations were both lower than the range used in testing helmets to the current football helmet standard. Because of this, researchers suggested lowering the pass/fail testing criteria for youth helmets to more accurately capture the magnitudes of impacts experienced by younger players on the field.
Ultimately the findings reported in this study helped support the development of a youth-specific helmet standard.
Where can I learn more about this study?Read the full study: “Brain Trauma Exposure for American Tackle Football Players 5 to 9 and 9 to 14 Years of Age – PDF.”
