Quantifying the biotribological properties of forehead skin to enhance head impact simulations

Head injury severity is dependent on the loading and accelerations experienced during, and immediately after, impact. In England and Wales alone, for example, 700,000 head injury cases are reported annually within Emergency Departments; however, there remains a lack of data that quantifies the fundamental interaction of the head with an impacting surface. The consequence of impact depends upon a precise understanding of the head–surface interaction; hence, there is a need to appreciate the magnitude of, and variation in, frictional coefficient between the head and a range of possible surfaces. This study develops and validates a novel protocol for quantifying friction between the forehead skin and some potential surfaces. Thirteen participants were recruited and four materials tested, with the lowest (0.11) and highest (1.64) dynamic frictional coefficients measured between skin, and expanded polystyrene and laminate flooring, respectively. Preliminary computational simulation identified that a modest variation in head–surface frictional coefficient (0.6 & 0.7) increases rotational accelerations by 23–33%. Hence, this study highlights the significance of the head–surface interaction, whilst providing some data that will assist investigators evaluating head impacts within both a domestic and sporting environment.