Football (soccer) is the most popular sport in the world. More than 265 million people play it. Billions more watch it. And for the vast majority of those players, at every level from Sunday morning grassroots to the elite professional game, it represents a profound source of joy, identity, and community. Which makes the science around head injuries in football not a reason to abandon the game – but a compelling reason to play it more intelligently.
This article explains how concussions happen in football, what the science shows about the longer-term risks of sub-concussive events, and why measurement, awareness, and smart training decisions matter more in football than perhaps any other sport in the world.
How the brain is injured in football
To understand concussion in football, it helps first to understand what a concussion actually is at the mechanical level.
The brain sits inside the skull, cushioned by cerebrospinal fluid. It is not rigidly fixed. When the head accelerates or decelerates very rapidly – through a collision, a heading duel, a fall, torso-to-torso contact, or a whiplash-type jolt – the brain momentarily lags behind the skull’s motion before the cerebrospinal fluid carries it along. That fraction-of-a-second lag causes the brain tissue to stretch, compress, and – critically – twist against the inside of the skull.
It is this twisting, shearing force – technically described as rotational or angular acceleration – that science increasingly identifies as the primary mechanical driver of brain injury. The brain has high resistance to compression but relatively low resistance to shear forces. When the head rotates quickly, brain tissue stretches and deforms in ways that can disrupt neural connections, damage axons, and trigger a cascade of cellular injury responses. A 2024 study on concussion biomechanics in sport confirmed that rotational head motion appears to be the primary contributor to brain injury risk, due to the unique mechanical properties of the brain and its location within the body.
The main causes of concussion in football
Unlike American football or rugby, football (soccer) does not immediately read as a high-contact sport. The reality, however, is more sobering. Concussion rates in football are comparable to, and often exceed, those of other contact sports traditionally considered as inherently more violent, such as American football and ice hockey. Up to 22% of all football injuries are concussions.
1. Player-to-player contact – the most common cause
The largest single cause of concussion in football is contact between players – typically head-to-head, elbow-to-head, or shoulder-to-head collisions when challenging for the ball. Head-to-player contact is the most common mechanism of injury, with defenders and midfielders having the highest total numbers of concussions, while goalkeepers have the highest risk relative to their numbers on the field. These collisions frequently occur during aerial duels – two or more players jumping to contest a high ball. The head movements involved are sudden, violent, and multidirectional, combining linear and rotational forces in ways that can cause significant brain movement inside the skull.
2. Heading the ball itself
Deliberate heading generates measurable forces on the brain. A football player can be subjected to an average of 6-12 incidents of heading per competitive game, where the ball reaches high velocities. In training sessions, heading repetitions are commonly far higher.
A recent 2024 study emphasised that ball-to-head impacts, especially those occurring at high speeds or short distances, are a prominent cause of mild traumatic brain injury in professional football athletes. Heading accounted for 30.5% of concussions in a prospective study of female middle-school football players. In a retrospective analysis of high-school players, heading was responsible for 30.6% of concussions among boys and 25.3% among girls – although the most frequent mechanism in heading-related concussions was player-to-player contact during the ball dispute.
This last point is important: the most dangerous heading events are often those where the player is also colliding with an opponent – making the combined force significantly greater than either heading alone or collision alone would produce.
3. Falls and ground contact
Falling – either from a challenge, a collision, or losing balance – can cause the head to strike the ground at significant force. Goalkeepers diving to save, outfield players being upended in a tackle, or simply slipping all represent moments when the head may accelerate toward a hard surface. Even when the head does not directly contact the ground, the rapid deceleration on landing can transmit significant forces to the brain.
4. Indirect jolts to the torso
This is less widely understood but equally important: a hard and sudden jolt to the torso – without any contact to the head at all – can generate sufficient body-to-head transmission of force to move the brain inside the skull. In a sport where physical contact across the body is routine, this represents a category of risk that is almost entirely invisible in standard concussion surveillance, because no head contact ever occurred.
Why football’s concussion problem is different from other sports
Several features of football create a distinctive risk profile:
Players are generally unprotected. Unlike American football or ice hockey, footballers wear no helmets. There is nothing to attenuate the peak forces of a collision, a stray elbow, or a head-to-ball contact.
Heading is a deliberate and valued skill. In most high-contact sports, head impacts are incidental – an unfortunate consequence of the physical nature of the game. In football, heading is trained, coached, and celebrated. Players are taught from childhood to use their heads as an elementary tool of the game.
The game is played globally at vast scale, including many young children. The sheer number of people playing football – and the age at which many begin – means the cumulative population-level exposure to head impacts is enormous compared with almost any other sport.
Symptoms are invisible and routinely played through. The culture of football has historically treated head impacts as unremarkable. Players who are clearly dazed after collisions continue playing. The absence of immediate pain – there are no pain receptors in brain tissue – makes it easy to minimise what may be a meaningful injury.
Sub-concussive events: the silent, accumulating risk
Here is where the picture in football becomes especially important – and where the science of the last decade has shifted the conversation fundamentally.
A concussion is a diagnosable event: something happened, and the player shows symptoms. Sub-concussive events are something different. They are the hundreds and thousands, of head acceleration events that occur in football – through heading, through collisions, through falls and more – that are individually below the threshold for any clinical symptom. The player play on. No one records anything. And yet the evidence is mounting that these events, accumulated over sessions, seasons and careers, are doing real and lasting damage.
What the imaging studies show
Imaging studies show white matter changes in players after a single season, even without a diagnosed concussion. Evidence from the British Journal of Sports Medicine, JAMA Pediatrics, the Boston University CTE Centre, and the NIH literature converges on one finding: sub-concussive exposure matters.
A 2025 study from Cardiff University used advanced diffusion MRI to track changes in brain white matter microstructure in university-level football players following a controlled heading protocol, measuring at intervals up to 180 days. Repetitive, sub-concussive head impacts have been associated with increased chronic traumatic encephalopathy (CTE) incidence.
Repetitive head impacts sustained in contact sports are thought to be necessary for the long-term development of CTE. And crucially, these impacts do not need to be concussive in their individual nature. The accumulation appears to be what matters.
A 2024 review by the Traumatic Brain Injury Centre of Excellence reported that multiple concussions and repetitive sub-concussive head impacts have been associated with altered white matter microstructure and blood-brain barrier disruption.
What the post-mortem studies show
The most unambiguous evidence comes from post-mortem brain examinations of former professional footballers who developed dementia in later life. A landmark study found that all six examined players had suffered from a tearing to a brain membrane consistent with chronic, repetitive head impacts from playing football. Four of the men had CTE, and the four diagnoses were probably related to their past prolonged exposure to repetitive head impacts from head-to-player collisions and heading the ball thousands of times throughout their careers.
A large-scale study of former professional footballers published in 2019 found they were 3.5 times more likely to die from dementia or other neurodegenerative diseases than matched controls from the general population. A 2017 study revealed that in six ex-football players, four had CTE with Alzheimer’s disease and two had Alzheimer’s disease alone. CTE pathology is uniquely linked to repeated head impact exposure, making it likely a key factor in dementia risk in former athletes.
It is important to note that not everyone who sustains repeated traumatic brain injuries or repetitive sub-concussive events will develop CTE. Not every footballer develops these conditions. The science does not say that playing football leads inevitably to dementia. What it says is that the risk is meaningfully elevated – and that the pathway runs through the accumulation of sub-concussive impacts over years, not only through the diagnosable concussions that happen to be recorded.
Heading and brain structure in amateur players
It is not only professionals who face risk. Research on 352 amateur football players aged 18 to 53 found abnormalities in the white matter surrounding the brain, particularly in the frontal lobe, similar to patterns seen in CTE – in players who had never been professional athletes.
The dose matters. How frequently a player heads the ball, how hard, and across how many years of a career all appear to influence the degree of accumulated risk. This is precisely why measuring and tracking head impact and event exposure – not just waiting for concussion symptoms to appear – represents a fundamentally different and more protective approach to athlete brain health.
What can actually be done
Understanding the problem is the first step. Acting on it is what makes the difference. There are things that every coach, team, club, parent, and player can do at every level of the game.
Reduce heading repetitions in training. Quality over quantity. The skill of heading can be developed with far fewer repetitions than many training programmes currently use. Each heading repetition in training is a sub-concussive event that contributes to cumulative load – but produces no improvement in the athlete’s competitive outcome.
Improve technique. A well-executed header – using the forehead, with the neck muscles braced – generates lower rotational forces than a poorly timed, off-balance one. Teaching proper technique, especially to young players, is not just a performance improvement; it is a brain protection strategy.
Never minimise a suspected concussion. Any player who shows signs of concussion – confusion, dizziness, headache, loss of consciousness however brief, or for example simply “not seeming right” – must leave the field immediately and not return. Same-day return to play is not safe at any level. This is not a grey area.
Take the sub-concussive load seriously. This is harder, because it requires changing the mental model of what matters. The athlete who has never had a diagnosed concussion may still be accumulating significant brain load across a season. Tracking that load objectively – using a head impact sensor – is the only way to make informed decisions about training intensity, match load, and recovery.
Measure and track what is actually happening. This is where technology like the ACT Head Impact Tracker becomes relevant. A sensor worn in a headband during training and matches records the number, magnitude, frequency, and proximity of every significant head acceleration event – giving coaches, physiotherapists, and athletes objective data that simply did not exist before. Not to diagnose injuries, but to manage exposure proactively over a career.
The bigger picture
Football is not going to stop being a contact sport. Heading is not going to be banned at senior level. Player-to-player collisions are an inherent part of a game played at speed. None of this means the risks are unmanageable – it means they need to be managed intelligently and with honesty.
The science is no longer speculative. The evidence linking repetitive head impacts – including, crucially, the sub-concussive events that generate no immediate symptoms – to measurable brain changes, elevated dementia risk, and in some cases CTE is substantial and growing risk. Researchers have now confirmed these findings in living players using advanced MRI, not only in post-mortem examination.
The pathway forward is not fear – it is knowledge. Knowing how, why, when and to whom impacts happen, how they accumulate, what makes them more or less dangerous, how to track them objectively and how influence them is what gives coaches, teams and clubs the power to genuinely improve the brain health and safety of every athlete who plays this remarkable game. There is no medication. There is no cure. Prevention – informed, consistent, measurable prevention – is the only tool available. And it works.
ACT Head Impact Tracker is a measurement device. ACT Head Impact Tracker is not a medical device. It does not provide medical advice, diagnostics, or treatment suggestions. In case of suspected head injury, immediately and safely remove the athlete from activity and seek assessment from a licensed medical professional.
For more information, or to buy your sensor, visit