Does Reduced Ball Inflation Pressure in Association Football Decrease Head Impact Kinematics?

Apparent degeneration in brain health due to heading the football is amongst the most pressing and contentious health-related questions in sport (Keogh F, Pirks N (2024) "Pain was sickening"-Ex-players on heading fears. In: BBC). The purpose of this study was to thoroughly explore the effectiveness of reduced inflation pressure as an intervention to reduce head kinematics from a ball to head impact. The influence of impact location, head orientation, neck flexion angle and ball type on the intervention were experimentally investigated.

A Hybrid III head and neck was impacted in frontal and oblique locations with two modern footballs that were projected using a bespoke launch device. Peak linear acceleration, peak angular velocity, peak angular acceleration and DAMAGE metrics were calculated for a total of 34 permutations of impact variables at two inflation pressures.

Magnitude was decreased (82%) or unchanged (8%) for 90% of impacts with average magnitude changes between - 2 and - 12% across the four metrics. Findings indicated that decreased inflation pressure was a positive intervention towards decreasing kinematic magnitudes in most cases. This was especially true for linear acceleration, angular velocity and angular acceleration, where 100, 97 and 100% of impacts were reduced or unchanged, respectively.

Reduced inflation pressure was overall an effective mitigation to reduce the kinematic magnitude of heading in football based upon these four kinematic metrics despite 10% of impacts exhibiting an increase in kinematic magnitude. The DAMAGE predictor of MPS exhibited 12 out of 13 cases where magnitude increased demonstrating the capacity for decreased inflation pressure to result in increased kinematics for an angular response derived metric, indicating that reducing inflation pressure is not a universal solution. Nonetheless DAMAGE still saw a net decrease in magnitude across all impacts. Metric magnitude was found to be sensitive to head orientation, impact location and ball type, demonstrating the importance of the sensitivity analysis in this study. Two impacts were recommended to represent the worst-case ball to head impact, one in each nominal orientation. These locations contrasted with those commonly used in literature, a finding pertinent to future experimental design in football heading research.