A Comparison of Youth Flag and Tackle Football Head Impact Biomechanics.

Our purpose was to describe the youth flag football head impact burden and make comparisons with youth tackle football. Head impact frequency and magnitude (linear acceleration [g], rotational acceleration [rad/s]) were collected from 25 tackle and 25 flag youth football players over one season. Athlete exposure (AE) was defined as one player participating in one session. Head impact rates (IR) were calculated and impact rate ratios (IRR) were used to compare youth tackle and flag football. Random-intercept generalized logit models with odds ratios compared the probabilities of sustaining an impact with a linear acceleration of 20.00-29.99, 30.00-39.99, and ≥40.00 against the reference of 14.00-19.99 and an impact with a rotational acceleration of 2500.00-7499.99 rad/s or ≥7500.00 rad/s against the reference of ≤2499.99 rad/s between youth flag and tackle football. We observed 1908 tackle football head impacts (735 in games, 38.5%) across 624 AE and 169 flag football head impacts (101 in games, 59.8%) across 255 AE. Youth tackle football players experienced higher overall IR (3.06, 95% confidence interval [CI]: 2.61, 3.58; IRR = 4.61, 95% CI: 3.94, 5.40) compared with flag football (IR = 0.66, 95% CI: 0.57, 0.78). Youth flag football players had lower odds of sustaining impacts >20 but higher odds of sustaining impacts between 2500.00-7499.99 rad/s compared with youth tackle players. Our preliminary sample of youth flag football players sustained less frequent head impacts at higher rotational accelerations than tackle football players. Flag football is considered a limited-contact sport, but little is known about the true head impact burden. Our findings may be important for policymakers when debating potential changes to youth football participation.