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

Abstract

<jats:sec><jats:title>OBJECTIVE</jats:title><jats:p>This study evaluated the frequency, magnitude, and location of head impacts in practice drills within a youth football team to determine how head impact exposure varies among different types of drills.</jats:p></jats:sec><jats:sec><jats:title>METHODS</jats:title><jats:p>On-field head impact data were collected from athletes participating in a youth football team for a single season. Each athlete wore a helmet instrumented with a Head Impact Telemetry (HIT) System head acceleration measurement device during all preseason, regular season, and playoff practices. Video was recorded for all practices, and video analysis was performed to verify head impacts and assign each head impact to a specific drill. Eleven drills were identified: dummy/sled tackling, install, special teams, Oklahoma, one-on-one, open-field tackling, passing, position skill work, multiplayer tackle, scrimmage, and tackling drill stations. Generalized linear models were fitted to log-transformed data, and Wald tests were used to assess differences in head accelerations and impact rates.</jats:p></jats:sec><jats:sec><jats:title>RESULTS</jats:title><jats:p>A total of 2125 impacts were measured during 30 contact practices in 9 athletes (mean age 11.1 ± 0.6 years, mean mass 44.9 ± 4.1 kg). Open-field tackling had the highest median and 95th percentile linear accelerations (24.7<jats:italic>g</jats:italic> and 97.8<jats:italic>g</jats:italic>, respectively) and resulted in significantly higher mean head accelerations than several other drills. The multiplayer tackle drill resulted in the highest head impact frequency, with an average of 0.59 impacts per minute per athlete, but the lowest 95th percentile linear accelerations of all drills. The front of the head was the most common impact location for all drills except dummy/sled tackling.</jats:p></jats:sec><jats:sec><jats:title>CONCLUSIONS</jats:title><jats:p>Head impact exposure varies significantly in youth football practice drills, with several drills exposing athletes to high-magnitude and/or high-frequency head impacts. These data suggest that further study of practice drills is an important step in developing evidence-based recommendations for modifying or eliminating certain high-intensity drills to reduce head impact exposure and injury risk for all levels of play.</jats:p></jats:sec>

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

“…This may partially be due to the amount of time spent on instructing the teams about game strategy, positioning, and so on. 21 In contrast, drills primarily focused on tackling and blocking, such as Oklahoma, had higher impact rates and only had instruction at the beginning and during brief intermittent pauses to correct technique. These results suggest that time spent on instruction and correcting technique may affect impact rate.…”

“…Prior studies have found that HIE significantly varies among practice drills, with full-speed tackling drills resulting in the highest head accelerations, and tackling or blocking drills with multiple player involvement resulting in the highest impact frequency. 10,21 Although these studies have provided insight into HIE in youth football practices, they were limited in size and did not account for variability among teams, which is an important factor since HIE can vary significantly among teams with the same age and weight restrictions. 22 The present study supports the results from prior investigations and determined that team has an effect on HIE in practice.…”

“…Open field tackling had the highest mean linear and rotational acceleration compared to all other drills evaluated in this study, which further supports a previous study that also found open field tackling to have the highest head accelerations. 21 A study of high-magnitude head impacts in youth football practices and games found that high-magnitude impacts (> 40g) occur most frequently in the open field in both games (59.4%) and practices (67.5%). 9 However, teams only practiced open field tackling 1-4 times in a season, with the exception of team E, which practiced this drill 12 times.…”

“…Prior studies have shown that there is significant variability in HIE among drills and that full-speed tackling drills result in the highest head impact severity. 10,21 However, past studies of HIE in practice drills were limited to single-season evaluations and a narrow age range; therefore, the objective of the present study was to use biomechanical data and video analysis to evaluate HIE in practice drills among 6 youth football teams and to determine the effect of individual teams on HIE in drills.…”

Cognitive Disorders Among Incoming College Football Athletes: Legal and Medical Implications of Undisclosed Inclusion in Concussion Research

“…83 Indeed, a recent study by Kelley et al found a total of 2,125 head impacts during 30 practices among 9 individual athletes whose mean age was 11.1 + 0.6 years. 84 The presence of modifying factors documented herein should be disclosed and controlled for in research on concussions, as the literature has observed for nearly two decades. The absence of such controls in the concussion research conducted at UNC raises questions about the validity of such studies and their applicability to other domains where head trauma is also the focus of interest.…”