For the first time, the men’s FIFA World Cup was played on Canadian soil, with Canada co-hosting alongside the United States and Mexico and matches at BMO Field in Toronto and BC Place in Vancouver. Amid the aerial duels, an old question returns: is heading a soccer ball bad for the brain? 

Canada made the World Cup knockout rounds for the first time in program history this year, a run that ended in the round of 16. Watching the aerial duels that punctuate World Cup matches, you wouldn’t be alone in wondering: how does heading a soccer ball affect the brain? Players head the ball roughly 80 times per match across both teams (Huber et al., 2024), yet a header rarely reaches the magnitudes associated with concussion; instead, the player-to-player collisions that happen while contesting the ball are the most common cause of head injury.

The kinematics of a header 

Two measurements describe how the head moves on impact. Linear, or translational, acceleration, expressed in multiples of gravity (g), captures how quickly the head is driven along a line. Rotational, or angular, acceleration, in radians per second squared, captures how quickly it is turned about an axis. Both come into play on any header, in proportions set by where and how the ball meets the skull. 

The brain is a soft, viscoelastic, and nearly incompressible structure that is suspended within the skull and far more tolerant of compression (squeezing) than of shear (smearing). Rapid loading produces injury primarily through shear strain due to stretching and distortion of neural tissue. Because of the fluid nature of the brain, both the magnitude and the rate of loading are related to concussion, and in extreme cases may result in diffuse axonal injury (DAI). Rapid rotation of the head couples efficiently into shear strain, which is why rotational acceleration carries particular weight for off-axis impacts. Linear motion contributes as well, and the most useful descriptions treat the two as acting together rather than in isolation (Rowson & Duma, 2013). 

By either measure, a single, well-struck header is a low-acceleration event. Controlled and on-field studies place a typical header in the region of 12 to 28 g, rising toward about 55 g when a player meets a ball driven from distance and into the low 60s in the hardest recorded youth headers (Naunheim et al., 2000, 2003; Hanlon & Bir, 2012; Kern et al., 2024). The contact is also brief and comparatively distributed, with a loading pulse on the order of twenty-five milliseconds (i.e., faster than the blink of an eye; Naunheim et al., 2003) spread across the area of the head that comes into contact with the deforming ball, rather than concentrated at a point. However, no two headers can be assumed to be the same. Ball speed, mass, and inflation pressure, the location of contact on the head, the player’s anticipation, and the bracing of the neck and trunk all shift the resulting kinematics, which is why technique and game situation matter as much as the act of heading itself (Shewchenko et al., 2005; Kern et al., 2024). 

Headers against the concussion range 

One widely cited estimate, pooled largely from American football, puts the average concussive impact near 100 g of linear acceleration, with a confidence interval of roughly 82 to 115 g (Brennan et al., 2017). More recent meta-analytic data place that average lower, near 70 g across all sports and about 83 g in American football (Ivanic et al., 2026), so the 100 g figure should be read as the upper end of the published estimates rather than a fixed threshold. Measured against that band, a header looks safe, and most fall far below it (Figure 1). The same review’s soccer-specific value is markedly lower, on the order of 52 g, although that estimate rests on only a handful of documented soccer concussions in the published biomechanics literature (Ivanic et al., 2026). At that value, the hardest headers no longer sit comfortably below it, and rotational values, which are more variable and harder to quantify outside a laboratory, can reach into the range associated with concussion as well. Younger players appear to tolerate less head acceleration than adults (Campolettano et al., 2020), which matters for the youth game. 

Figure 1: Header accelerations versus concussive impact averages. Two header datasets, on-field girls’ youth soccer (Hanlon & Bir, 2012) and controlled adult-male heading (Naunheim et al., 2003), sit well below the football-derived concussive mean on the linear measure (Brennan et al., 2017); the soccer-specific concussive mean is markedly lower, about 52 g (Ivanic et al., 2026). Rotational values overlap the concussive range, yet the rare headers that reached it produced no diagnosed concussion. These are group means, not injury thresholds. 

Where the injury comes from 

A national analysis of concussions in young soccer players found player-to-player contact to be the most common cause, and player-to-player and head-to-ground contact to account for the great majority of concussions requiring hospitalization, with head-to-ball contact carrying by far the lowest risk (Chatha et al., 2020). On-field measurement in youth players points the same way: purposeful headers were low-acceleration events, and the non-heading impacts recorded were dominated by player-to-player collisions rather than the ball (Hanlon & Bir, 2012). Rising for a cross is simply the moment at which two heads, a head and an elbow, or a head and the turf are most likely to meet, and a head-to-head collision readily generates the focal, often unanticipated loading that a controlled header does not. Heading and the mechanism of injury are related but not identical, and conflating them leads to a wrong conclusion. 

The unresolved question of cumulative exposure 

The open question is not the effect of a single header but the sum of them all, with an important distinction in mind. An acute, symptomatic concussion is a different phenomenon from the repetitive subconcussive loading that repeatedly heading a ball represents. It is the long-term effect of the latter that remains genuinely unsettled. The volume is not trivial. As mentioned previously, elite men’s matches average roughly 80 headers across both teams, with more in some domestic leagues (Huber et al., 2024), which over a career represents thousands of contacts. The most influential evidence comes from the FIELD study at the University of Glasgow, which found that former professional footballers died of neurodegenerative disease at about three and a half times the expected rate, with risk rising as career length increased, particularly amongst defenders (Mackay et al., 2019; Russell et al., 2021, 2024). This evidence is associative rather than a demonstrated dose-response from heading alone, and it carries the usual cautions of observational research, but it has been consequential: it informed the U.S. Soccer Federation’s 2015 restrictions on heading for children aged ten and under and the English Football Association’s phased removal of deliberate heading from youth matches through the under-eleven level (The Football Association, 2024).

Soccer

Why this matters off the pitch 

At 30 Forensic Engineering, experts in our Biomechanics & Personal Injury group are regularly retained to assess injury causation, and the header is a useful illustration of how that work is approached. The aim is to characterize the mechanism rather than simply the magnitude: what struck the head, under what conditions, and how the event compares with the most appropriate reference data, matched both to the right population and to the way those reference values were obtained. A sound biomechanical opinion therefore works from the evidence available, distinguishes the loading that actually occurred from the category it belongs to, and is candid about the limits of what can be quantified.

So as the tournament continues, the takeaway is narrow and useful. The biomechanical science indicates that heading a soccer ball is rarely the problem. However, the long-term effects of cumulative header exposure remain uncertain, and that is where the work, and the policy, are still being written.

Chad Gooyers, Ph.D., MBA, P.L.Eng.(EGBC), is Technical Director, Biomechanics and Personal Injury, and Regional Director, Western Canada, at 30 Forensic Engineering. He has nearly two decades of research and forensic experience in injury causation biomechanics, occupant restraint systems, and helmet effectiveness, holds an academic appointment at the University of Waterloo, and has been qualified to provide expert evidence before the British Columbia Supreme Court and the Ontario Superior Court of Justice. 

 
References 

Brennan, J. H., Mitra, B., Synnot, A., McKenzie, J., Willmott, C., McIntosh, A. S., Maller, J. J., & Rosenfeld, J. V. (2017). Accelerometers for the assessment of concussion in male athletes: A systematic review and meta-analysis. Sports Medicine, 47(3), 469-478.  

Campolettano, E. T., Gellner, R. A., Smith, E. P., Bellamkonda, S., Tierney, C. T., Crisco, J. J., Jones, D. A., Kelley, M. E., Urban, J. E., Stitzel, J. D., Genemaras, A., Beckwith, J. G., Greenwald, R. M., Maerlender, A. C., Brolinson, P. G., Duma, S. M., & Rowson, S. (2020). Development of a concussion risk function for a youth population using head linear and rotational acceleration. Annals of Biomedical Engineering, 48(1), 92-103.  

Chatha, K., Pruis, T., Fernandez Peaguda, C., Guo, E., Koen, S., Malone, D., & Sabesan, V. (2020). Concussions in soccer: An epidemiological analysis in the pediatric population. Orthopaedic Journal of Sports Medicine, 8(10), 2325967120951077.  

Hanlon, E. M., & Bir, C. A. (2012). Real-time head acceleration measurement in girls’ youth soccer. Medicine & Science in Sports & Exercise, 44(6), 1102-1108.  

Huber, L., Szymski, D., Krutsch, W., Alt, V., & Weber, J. (2024). Video analysis of heading and risk of head injury situations in elite international men’s football: Does the frequency of headers increase with the level of play? European Journal of Sport Science, 24(4), 518-524.  

Ivanic, B., Cronström, A., Rasi, M., & Ageberg, E. (2026). Head acceleration magnitude in sport-related concussive impacts: A systematic review and meta-analysis. Sports Medicine. Advance online publication.  

Kern, J., Hermsdörfer, J., & Gulde, P. (2024). Factors influencing wearable-derived head impact kinematics in soccer heading. German Journal of Sports Medicine, 75(3), 105-112.  

Mackay, D. F., Russell, E. R., Stewart, K., MacLean, J. A., Pell, J. P., & Stewart, W. (2019). Neurodegenerative disease mortality among former professional soccer players. New England Journal of Medicine, 381(19), 1801-1808.  

Naunheim, R. S., Bayly, P. V., Standeven, J., Neubauer, J. S., Lewis, L. M., & Genin, G. M. (2003). Linear and angular head accelerations during heading of a soccer ball. Medicine & Science in Sports & Exercise, 35(8), 1406-1412.  

Naunheim, R. S., Standeven, J., Richter, C., & Lewis, L. M. (2000). Comparison of impact data in hockey, football, and soccer. The Journal of Trauma: Injury, Infection, and Critical Care, 48(5), 938-941.  

Rowson, S., & Duma, S. M. (2013). Brain injury prediction: Assessing the combined probability of concussion using linear and rotational head acceleration. Annals of Biomedical Engineering, 41(5), 873-882.  

Russell, E. R., Mackay, D. F., Stewart, K., MacLean, J. A., Pell, J. P., & Stewart, W. (2021). Association of field position and career length with risk of neurodegenerative disease in male former professional soccer players. JAMA Neurology, 78(9), 1057-1063.  

Russell, E. R., Lyall, D. M., Mackay, D. F., Cronin, K., Stewart, K., MacLean, J. A., Pell, J. P., & Stewart, W. (2024). Health and lifestyle factors and dementia risk among former professional soccer players. JAMA Network Open, 7(12), e2449742.  

Shewchenko, N., Withnall, C., Keown, M., Gittens, R., & Dvorak, J. (2005). Heading in football. Part 1: Development of biomechanical methods to investigate head response. British Journal of Sports Medicine, 39(Suppl. 1), i10-i25.  

The Football Association. (2024, May 17). New heading rules for U7 to U11 youth football. England Football.

U.S. Soccer Federation. (2015). U.S. Soccer concussion initiative: Recognize to Recover player health and safety program.