The relationship between mechanical properties and dynamic behaviour: A data-driven exploratory analysis of football impact behaviour

This study presents a data-driven exploratory analysis that combines experimental measurements with statistical modelling to investigate how the mechanical properties of a football, specifically stiffness and energy loss, influence a football’s impact behaviour. Experimental testing of twelve FIFA-certified footballs, impacted at low (5.93 ± 0.06 m s−1) and high (19.2 ± 0.4 m s−1) velocities, revealed three distinct characterisations of impact behaviour. These groupings were primarily defined by contact time and deformation, variables that were strongly correlated with the stiffness properties of the balls, measured in both static and dynamic environments. Multivariable models were developed using inputs of impact conditions and ball properties. For the selected outcome variables (contact time and deformation) and under the conditions tested, these inputs could explain up to 96% of the differences observed in impact behaviour in the best-performing model. The models also demonstrated agreement with observed behaviour in an independent dataset, in this instance errors of 2.8% (corresponding to 0.3 ms) were observed for contact time and errors of 3.4%–9.7% (corresponding to 1–5.5 mm) were observed for deformation. Properties of the footballs measured at the low velocity also demonstrated reasonable consistency in their relationship with dynamic impact behaviours at the higher velocity with errors below 7%. This study demonstrates the use of statistical modelling to classify and explain aspects of football impact behaviour using a small set of measurable properties, within the conditions investigated.