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

Abstract

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.

Head impact exposure measured in a single youth football team during practice drills

“…Several studies have shown that football players in older age groups (i.e., high school and college) experience higher-severity impacts more frequently, so further study of HIE in drills in older age groups would also increase our understanding of practice-related HIE and injury risk. 7,17 The impact rate metric, impacts per minute per player, only takes into account measured impacts; it does not consider instances of no impact while participating in the drill. Lastly, the HIT System, which was used for bio-mechanical data collection, has some measurement error, but the error in 5 degrees of freedom (5DOF) acceleration measurements are within the range of acceptable error for other measurement devices and methods.…”

“…Although the amount of available HIE data for youth-level football players has been limited, compared with data for high school and college players, there have been notable findings from past studies. 9,17,28,31–33 Results from several studies showed that youth football players sustain head impacts approaching the magnitude of those sustained by high school and college football players. 9,11,39 A study of HIE in youth football athletes aged 7–8 years showed that the majority of high-level impacts (> 80 g ) occur during practice rather than games.…”

Comparison of head impact exposure in practice drills among multiple youth football teams

“…33,37,38,40 Collecting on-field head impact data from collegiate, high school, and youth football athletes has improved our understanding of head impact biomechanics in football. 5,14,22,43 With approximately 70% of athletes playing youth football, there has been a greater focus recently on studying HIE in this population. Studies have shown that youth athletes experience high-magnitude head impacts (> 80g) in practices and games, similar to their older counterparts.…”

“…Studies have shown that youth athletes experience high-magnitude head impacts (> 80g) in practices and games, similar to their older counterparts. 9,12,22 Youth football spans the ages of 5 to 13 years, and teams are often defined by age and/or weight. A recent study found that younger football players (ages [10][11] are more frequently exposed to high-magnitude impacts in practices, whereas older youth football players (ages 12-13) are exposed to more high-magnitude impacts in games; 22 however, the majority of head impacts occur in practice rather than games for most athletes.…”

“…A recent study found that younger football players (ages [10][11] are more frequently exposed to high-magnitude impacts in practices, whereas older youth football players (ages 12-13) are exposed to more high-magnitude impacts in games; 22 however, the majority of head impacts occur in practice rather than games for most athletes. 12,15,22 On-field head impact data have been used to inform evidence-based rule changes to reduce HIE and evaluate the effectiveness of rule changes. 6,12,15 Prior efforts to reduce HIE have primarily focused on reducing the amount of time allowed for contact in practice.…”