Head Impact Exposure of Youth Football Players During Their 7th and 8th Grade Seasons

Abstract

Nearly 70% of US football players are younger than high school age, yet little is known about the potentially damaging effects of repetitive head impacts in this population. Cross-sectional studies indicate that head impact exposure increases with older levels of play, though little is known about changes in the same group of players from year to year. PURPOSE: To evaluate changes in head impact exposure among youth football players between their 7th and 8th grade seasons. METHODS: During a five-year span (2012-2016), head impact exposure of thirty middle school football players (12.6 ± 0.4 yr) was assessed during their 7th and 8th grade seasons while participating in a community tackle football program. Subjects played on the same team during their 7th and 8th grade seasons. Head impact frequency, severity (linear acceleration [LA]; rotational acceleration [RA]) and location during each practice and game were measured using the Head Impact Telemetry (HIT) system, consisting of a helmet-mounted accelerometry array. RESULTS: Mean head impacts per player were significantly higher in practices (7.4 vs. 5.8 impacts / player; P = 0.035) but not significantly different in games (10.1 vs. 12.4 impacts / player; P = 0.134) comparing the 7th to 8th grade seasons, respectively. Furthermore, from the 7th to 8th grade season, mean LA (25.30 g vs. 25.95 g; P = 0.345), median LA (20.77 g vs. 21.39 g; P = 0.225), mean RA (1741 rad • sec-2 vs. 1744 rad • sec-2; P = 0.950) and median RA (1481 rad • sec-2 vs. 1503 rad • sec-2; P = 0.538) did not differ significantly. Finally, no differences in distribution of head impacts by location (Front: 46% vs. 48%; P = 0.461; Top: 10% vs. 11%; P = 0.607; Back: 26% vs. 23%; P = 0.159; Right: 9% vs. 10%; P = 0.382; Left: 8% vs. 8%; P = 0.717) were found between the 7th and 8th grade seasons, respectively. CONCLUSIONS: Individual head impact exposure was similar during two consecutive seasons of youth football, despite increased age and playing experience during the second season. Thus, extrinsic factors such as game rules, practice structure and coaching style may have a greater influence on head impact exposure from year to year in youth football, making those aspects of play key targets for strategies aimed at reducing repetitive head impacts in this population.