Force experienced by the head during heading is influenced more by speed than the mechanical properties of the football

Abstract

There are growing concerns about the risk of neurodegenerative diseases associated with heading in football. It is essential to understand the biomechanics of football heading to guide player protection strategies to reduce the severity of the impact. The aim of this study was to assess the effect of football speed, mass, and stiffness on the forces experienced during football heading using mathematical and human body computational model simulations. Previous research indicates that a football header can be modeled as a lumped mass mathematical model with elastic contact. Football headers were then reconstructed using a human body modeling approach. Simulations were run by independently varying the football mass, speed, and stiffness. Peak contact force experienced by the head was extracted from each simulation. The mathematical and human body computational model simulations indicate that the force experienced by the head was directly proportional to the speed of the ball and directly proportional to the square root of the ball stiffness and mass. Over the practical range of ball speed, mass, and stiffness, the force experienced by the head during football heading is mainly influenced by the speed of the ball rather than its mass or stiffness. The findings suggest that it would be more beneficial to develop player protection strategies that aim to reduce the speed at which the ball is traveling when headed by a player. Law changes reducing high ball speeds could be trialed at certain age grades or as a phased introduction to football heading.

Immediate effects of an acute bout of repeated soccer heading on cognitive performance

“…With this in mind, the head impacts appeared surprisingly low compared to previous accounts of heading that have used a similar accelerometer measurement (Shewchenko et al 2005). Presumably, these comparatively low values were attributed to our ball serving protocol (Tierney et al 2020), where players would receive a straight-line ball toss as opposed to a preallocated serving velocity from a ball projection machine (e.g., Di Virgilio et al 2016). That said, there was still a sufficient amount of accelerative head impact such that the heading groups were much higher than the control group.…”

The incidence and mechanism of heading in European professional football players over three seasons

“…The greatest distance travelled by the football was during goal kicks, which accounted for up to 11.5% of headers for forwards. These types of preceding match events are likely to cause the most severe header impacts due to the higher velocity the football travels at, 6 reaching speeds up to 85 km/h (23.6 m/s) 24 . Goal kick rule changes could provide an opportunity to decrease the maximum football velocities at which players head the ball at.…”

“…No heading in primary school age pupils and a graduated approach to heading in children aged between 12 and 16 during training was advised 5 . A recent study found that these policy changes could be further enhanced by replacing goal kicks which result in the highest heading ball speeds, and hence greatest head contact forces, with throws or head‐height rules at certain age grades as part of a phased introduction to heading 6 . Many studies reconstruct football headers in a laboratory environment to measure acute clinical changes 7,8 .…”

Soccer heading immediately alters brain function and brain-muscle communication

“…Whilst this pressure reflects the upper limit recommended by IFAB, it exceeds the max pressure of 15.2 psi recommended by the FA and may therefore question the generalisability of our findings. However, recent evidence from simulations indicate that the force experienced by the head is more impacted by the speed of the ball rather than its mass or stiffness ( Tierney et al, 2021 ). There was also no follow-up testing to ascertain when these changes in cortical and corticomuscular function dissipated.…”