Investigation of the effect of wearing protective headgear and ball pressure on the head response and brain deformation in soccer heading / Tan Fu Yang

Faculty of Mechanical and Automotive Engineering Technology

Thesis (Master of Science) -- Universiti Malaysia Pahang – 2024

Includes bibliographical references

Soccer, the world's most beloved sport, captivates over 4 billion fans globally. However, this exhilarating game is not without its risks. One contributing factor is the widely practiced technique of heading, where players use their heads to redirect the ball's trajectory. While this maneuver is integral to the sport, it carries an inherent risk of concussions and other head-related injuries. In an effort to mitigate these risks, the use of protective headgear has gained widespread acceptance among soccer players. However, the effectiveness of such headgear in reducing the impact sustained during heading remains poorly understood and lacks comprehensive definition. Additionally, there is a belief that decreasing soccer ball pressure could contribute to a decreased risk of injury. Mounting evidence suggests that repeatedly heading a soccer ball can negatively alter brain structure and function over time. Therefore, this study aimed to investigate the effectiveness of two soccer headgear models (Full90 and ForceField) in minimizing the risk of head injuries and brain deformation, as well as the effects of varying ball inflation pressures (0.6 bar, 0.8 bar, and 1.0 bar) on these factors. To achieve this, biomechanical reconstructions of ball-to-head impacts were conducted using an anthropomorphic testing device consisting of a head and neck, fitted with sensors (accelerometer and gyroscope) at the center of gravity of the headform. Soccer heading experiments were performed by launching soccer balls from a ball launcher towards the forehead of the anthropomorphic testing device. To evaluate brain deformation, finite element analysis was performed using a validated human head finite element model, with the recorded sensor data from the experiments serving as boundary conditions at the center of gravity. The primary head injury parameters considered were peak linear acceleration, peak rotational acceleration, Head Injury Criterion (HIC), and Rotational Injury Criterion (RIC). For brain deformation analysis, the key values extracted were Maximum Principal Strain and von Mises Stress, specifically from the cerebrum. The impact test results across all soccer headgear revealed no significant attenuation in peak linear acceleration, peak rotational acceleration, HIC, Maximum Principal Strain, and von Mises Stress. These findings indicate that the tested soccer headgear did not effectively reduce the incidence or severity of head injuries or brain deformation in soccer players. This outcome can likely be attributed to the considerable deformation of the soccer ball relative to the thickness of the headgear. As a result, further research efforts should focus on refining headgear design and incorporating advanced composite materials. Additionally, the study highlighted that the soccer ball inflation pressure of 0.8 bar led to an increase in specific head injury parameters, specifically peak linear acceleration and HIC, underscoring the complexity of this issue. Reducing the ball pressure to 0.6 bar did not yield any significant decreases in injury parameters. Consequently, future studies should expand the scope of ball inflation pressure investigation beyond FIFA regulations, covering a broader range of ball inflation pressures to gain a comprehensive understanding of its impact on player safety.