Heading in football. Part 3: effect of ball properties on head response.
OBJECTIVE
Head impacts from footballs are an essential part of the game but have been implicated in mild and acute neuropsychological impairment. Ball characteristics have been noted in literature to affect the impact response of the head; however, the biomechanics are not well understood. The present study determined whether ball mass, pressure, and construction characteristics help reduce head and neck can impact response.


METHODS
Head responses under ball impact (6-7 m/s) were measured with a biofidelic numerical human model and controlled human subject trials (n = 3). Three ball masses and four ball pressures were investigated for frontal heading. Further, the effect of ball construction in wet/dry conditions was studied with the numerical model. The dynamic ball characteristics were determined experimentally. Head linear and angular accelerations were measured and compared with injury assessment functions comprising peak values and head impact power. Neck responses were assessed with the numerical model.


RESULTS
Ball mass reductions up to 35% resulted in decreased head responses up to 23-35% for the numerical and subject trials. Similar decreases in neck axial and shear responses were observed. Ball pressure reductions of 50% resulted in head and neck response reductions up to 10-31% for the subject trials and numerical model. Head response reductions up to 15% were observed between different ball constructions. The wet condition generally resulted in greater head and neck responses of up to 20%.


CONCLUSIONS
Ball mass, pressure, and construction can reduce the impact severity to the head and neck. It is foreseeable that the benefits can be extended to players of all ages and skill levels.
Shewchenko
N
N
Biokinetics and Associates Ltd, Ontario, Canada. shewchenko@biokinetics.com
Withnall
C
C
Keown
M
M
Gittens
R
R
Dvorak
J
J
D001696:Biomechanical Phenomena / Q000379:methods; D004867:Equipment Design / Q000009:adverse effects / Q000592:standards; D016489:Head Injuries, Closed / Q000209:etiology*; D019416:Head Movements / Q000502:physiology*; D006801:Humans; D015601:Injury Severity Score; D008962:Models, Theoretical; D011187:Posture / Q000502:physiology; D012307:Risk Factors; D012916:Soccer / Q000293:injuries* / Q000502:physiology; D019876:Sports Equipment / Q000009:adverse effects / Q000592:standards