Head Impact Biomechanics in Youth Flag Football: A Prospective Cohort Study.
BACKGROUND
Youth flag football participation has rapidly grown and is a potentially safer alternative to tackle football. However, limited research has quantitatively assessed youth flag football head impact biomechanics.


PURPOSE
To describe head impact biomechanics outcomes in youth flag football and explore factors associated with head impact magnitudes.


STUDY DESIGN
Cross-sectional study; Level of evidence, 3.


METHODS
We monitored 52 player-seasons among 48 male flag football players (mean ± SD; age, 9.4 ± 1.1 years; height, 138.6 ± 9.5 cm; mass, 34.7 ± 9.2 kg) across 3 seasons using head impact sensors during practices and games. Sensors recorded head impact frequencies, peak linear (g) and rotational (rad/s2) acceleration, and estimated impact location. Impact rates (IRs) were calculated as 1 impact per 10 player-exposures; IR ratios (IRRs) were used to compare season, event type, and age group IRs; and 95% CIs were calculated for IRs and IRRs. Weekly and seasonal cumulative head impact frequencies and magnitudes were calculated. Mixed-model regression models examined the association between player characteristics, event type, and seasons and peak linear and rotational accelerations.


RESULTS
A total of 429 head impacts from 604 exposures occurred across the study period (IR, 7.10; 95% CI, 4.81-10.50). Weekly and seasonal cumulative median head impact frequencies were 1.00 (range, 0-2.63) and 7.50 (range, 0-21.00), respectively. The most frequent estimated head impact locations were the skull base (n = 96; 22.4%), top of the head (n = 74; 17.2%), and back of the head (n = 66; 15.4%). The combined event type IRs differed among the 3 seasons (IRR range, 1.45-2.68). Games produced greater IRs (IRR, 1.24; 95% CI, 1.01-1.53) and peak linear acceleration (mean difference, 5.69g; P = .008) than did practices. Older players demonstrated greater combined event-type IRs (IRR, 1.46; 95% CI, 1.12-1.90) and increased head impact magnitudes than did younger players, with every 1-year age increase associated with a 3.78g and 602.81-rad/s2 increase in peak linear and rotational acceleration magnitude, respectively (P≤ .005).


CONCLUSION
Head IRs and magnitudes varied across seasons, thus highlighting multiple season and cohort data are valuable when providing estimates. Head IRs were relatively low across seasons, while linear and rotational acceleration magnitudes were relatively high.
['Lempke|Landon B|LB|', 'Johnson|Rachel S|RS|', 'Le|Rachel K|RK|', 'Anderson|Melissa N|MN|', 'Schmidt|Julianne D|JD|', 'Lynall|Robert C|RC|']
D000054:Acceleration D000293:Adolescent D001696:Biomechanical Phenomena D001924:Brain Concussion D002648:Child D015331:Cohort Studies D003430:Cross-Sectional Studies D005538:Football D006257:Head D006260:Head Protective Devices D006801:Humans D008297:Male D011446:Prospective Studies
concussion pediatric repetitive head impact sport safety subconcussive youth sport