What did I do? -I investigated head acceleration during purposeful football heading across age and sex and determinants of head impact severity. Why did I do it? -Nearly 4% of the world`s population plays football, including over 26 million women. Although there are unrefuted positive health effects of playing football,1 chronic traumatic encephalopathy (CTE) has been identified in three football players,2 including British player, Jeffrey Astle, causing concern about the long-term effects of repetitive heading. To prevent or mitigate the effects of repetitive football heading, I believe that we must understand the biomechanics and identify strategies for reducing head impact severity.3 Currently, the little information on the biomechanical response to purposeful heading is limited to collegiate male football players, but these data may not be transferable to women and children, who have lower head mass, decreased neck muscle mass/strength and potentially underdeveloped heading skills.4 With inadequate research on football heading biomechanics and modifying factors among women and children, I believe that there may be unknown consequences of frequent heading in these groups. How did I do it? - I recruited 100 football players (42 male, 58 female, 17.1±3.5 years, 168.5±20.3cm, 61.5±13.7kg) to complete 12 controlled football headers (footballs=size 5, 450 g, 9psi; initial velocity=11.2 m/s; projection angle=40°). For each participant, 10 determinants of head impact severity were identified. Head mass was defined as a percentage of total body weight. Neck girth was defined as the circumference above the thyroid cartilage. Sternocleidomastoid and upper trapezius isometric strength were measured using a handheld dynamometer. Trunk and head-to-trunk kinematics were determined using a motion capture system. Sternocleidomastoid and upper trapezius activity, peak and area were calculated from electromyography (EMG). Comparison across age and sex: Peak linear and rotational head accelerations were compared by sex (female, male) and age (collegiate, high school, youth). Determinants of head impact severity: Multiple regression analyses were conducted to determine if size (head mass and neck girth), strength (sternocleidomastoid and upper trapezius) or technique (kinematics and EMG activity) variables predicted the peak linear and rotational head accelerations. What did I find? - Regarding comparisons across age and sex, I found that female football players produced higher peak linear and rotational head accelerations than male football players, but there were no significant differences across age
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