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J Neurotrauma. 2017 Jun 1;34(11):1939-1947. doi: 10.1089/neu.2016.4812. Epub 2017 Apr 7.

Head Impact Exposure in Youth Football: Comparing Age- and Weight-Based Levels of Play.

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1 Department of Biomedical Engineering, Wake Forest School of Medicine , Winston-Salem, North Carolina.
2 Virginia Tech - Wake Forest School of Biomedical Engineering and Sciences , Winston-Salem, North Carolina.
3 Department of Biostatistical Sciences, Wake Forest School of Medicine , Winston-Salem, North Carolina.
4 Department of Radiology, University of Texas Southwestern , Dallas, Texas.
5 Department of Radiology (Neuroradiology), Wake Forest School of Medicine , Winston-Salem, North Carolina.
6 Clinical and Translational Sciences Institute , Wake Forest School of Medicine, Winston-Salem, North Carolina.


Approximately 5,000,000 athletes play organized football in the United States, and youth athletes constitute the largest proportion with ∼3,500,000 participants. Investigations of head impact exposure (HIE) in youth football have been limited in size and duration. The objective of this study was to evaluate HIE of athletes participating in three age- and weight-based levels of play within a single youth football organization over four seasons. Head impact data were collected using the Head Impact Telemetry (HIT) System. Mixed effects linear models were fitted, and Wald tests were used to assess differences in head accelerations and number of impacts among levels and session type (competitions vs. practices). The three levels studied were levels A (n = 39, age = 10.8 ± 0.7 years, weight = 97.5 ± 11.8 lb), B (n = 48, age = 11.9 ± 0.5 years, weight = 106.1 ± 13.8 lb), and C (n = 32, age = 13.0 ± 0.5 years, weight = 126.5 ± 18.6 lb). A total of 40,538 head impacts were measured. The median/95th percentile linear head acceleration for levels A, B, and C was 19.8/49.4g, 20.6/51.0g, and 22.0/57.9g, respectively. Level C had significantly greater mean linear acceleration than both levels A (p = 0.005) and B (p = 0.02). There were a significantly greater number of impacts per player in a competition than in a practice session for all levels (A, p = 0.0005, B, p = 0.0019, and C, p < 0.0001). Athletes at lower levels experienced a greater percentage of their high magnitude impacts (≥ 80g) in practice, whereas those at the highest level experienced a greater percentage of their high magnitude impacts in competition. These data improve our understanding of HIE within youth football and are an important step in making evidence-based decisions to reduce HIE.


biomechanics; football; impact frequency; impact magnitude; mild traumatic brain injury; pediatric

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