Ice hockey is one of the most physically demanding sports in the world. Players travel at speeds up to 50 km/h on a hard surface enclosed by boards and glass, carrying sticks, wearing skates, and competing in a game that prizes physical strength as much as skill. It is also, by almost any measure, one of the highest-risk sports for head injury.
Yet for all the attention paid to individual concussions – the spectacular collision, the player helped off the ice, the weeks missed – the evidence emerging from science over the last decade suggests that the bigger risk may be something quieter, harder to see, and far more pervasive: the accumulation of hundreds or thousands of smaller head impacts and events across a season and a career that never individually register as injuries at all.
This article explains the mechanics of how concussions happen in ice hockey, who is most at risk, what the new science on sub-concussive events reveals, and what can be done to protect the brains of every athlete who plays this sport.
How the brain is injured in ice hockey
The brain floats inside the skull in cerebrospinal fluid. It is not attached to the skull’s inner surface. When the head moves suddenly – accelerating, decelerating, or rotating rapidly – the brain momentarily lags behind before being dragged along by the surrounding fluid and tissue. That lag causes the brain to move, compress, and twist against the inside of the skull.
It is the twisting – the rotational component – that science increasingly identifies as the primary driver of brain tissue damage. The brain’s mechanical properties make it far more vulnerable to shear forces generated by rotation than to direct compression forces. A 2025 review 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.
Ice hockey generates these forces in multiple ways and at velocities that are unusually high compared with most other sports. A player skating at full speed who collides with another player, the boards, or the ice does not just experience a force to one part of the body – the entire system absorbs and transfers that energy, and a significant portion of it reaches the brain.
The main causes of concussion in ice hockey
1. Body checking – and the blindside hit
Body checking is fundamental to ice hockey at the adult competitive level, and the single largest source of concussion in the sport. What makes checking particularly dangerous for the brain is not the force of intended, straight-line contact – it is the unexpected, rotational forces generated by hits the player does not anticipate.
A blindside hit – where a player is struck from the side or from behind without seeing the contact coming – is especially damaging because the neck muscles have no time to brace. The head is effectively flung by the sudden momentum transfer, generating the rotational acceleration that research consistently identifies as the most injurious force acting on the brain. Checking from behind drives the player into the boards or the ice at high speed, combining body deceleration with secondary head contact at a surface that does not give.
2. Head contact with the boards and glass
The rink’s rigid perimeter – boards below, plexiglass above – is one of the sport’s most distinctive and most dangerous features from a brain injury perspective. When a player is driven into the boards, the sudden deceleration can be more forceful than the original check, because the boards do not absorb impact the way a human body does. Head contact with the boards, whether from a check, a fall, or an awkward collision, is the most common cause of hospitalisation in youth ice hockey concussion data. The angle and speed of impact, which part of the boards the head contacts, and whether the player was braced for the contact all influence the severity. A player driven head-first into the boards at full speed by a check from behind represents one of the highest-energy impact scenarios in sport.
3. Falls to the ice
The ice surface is hard, flat, and unforgiving. A fall – from a trip, a collision, losing an edge, or being knocked off balance – can cause the head to strike the ice directly, or cause the neck to absorb a violent deceleration that transmits force to the brain even without direct head contact. Head contact with the ice is the most common mechanism of concussion in youth ice hockey, appearing more frequently in studies than checking-related injuries for younger age groups where body checking is restricted or absent.
This is particularly relevant for women’s hockey. At the collegiate level in the United States, women’s hockey has the highest concussion incident rate across all female collegiate sports. In women’s ice hockey, player-to-player collisions account for around 50% of all head impacts, and falls to the ice are also a major source – and because body checking has historically not been part of women’s hockey training, many players are less practised in anticipating and absorbing body contact, which can make unexpected collisions more dangerous.
4. Stick and puck contact
Although less common than contact with players, boards, or ice, head contact from a stick – whether from a high stick, a cross-check, or an accidental swing – and from puck impacts represent real injury mechanisms. Head contact from a puck travelling at professional speeds can exceed 160 km/h, and the force involved, concentrated on a very small surface area, can generate significant acceleration.
5. Collisions without body contact
This is the category that surprises many people, but the physics are straightforward: a rapid jolt to the torso – from a collision, a fall on the shoulder, or a hit absorbed by the body – can transmit sufficient force up the spine to cause the head to accelerate rapidly, moving the brain inside the skull. No head contact occurred. But the brain still moved. The forces generated by high-speed collisions in ice hockey are frequently transmitted through the body in ways that do not require the head to be the primary point of contact.
Ice hockey’s specific risk factors
Several features of ice hockey create a particularly high-risk environment for brain injury.
Speed amplifies everything. The combination of skating speed and physical contact means forces in ice hockey impacts are substantially higher than in many other contact sports. A check that would be unremarkable in a slower sport can generate significant brain acceleration at full skating speed.
The hard perimeter is unique to the sport. No other major contact sport has the combination of speed, physical contact, and a hard surrounding boundary. The boards and glass create a category of secondary impact – player driven into an immovable surface – that simply does not exist at the same scale in football, rugby, or basketball.
Helmets protect the skull, not the brain. Standard ice hockey helmets are effective at reducing skull fractures and laceration injuries. They offer limited protection against the forces that drive brain injury.
The culture of playing through. Ice hockey has a long cultural tradition of toughness and playing hurt. Players have historically returned to the ice after impacts that left them visibly dazed. This culture is changing at the elite level, but it persists in amateur and youth hockey, where medical oversight may be limited or absent.
Youth exposure begins early. In Finland, Canada, Sweden, and other hockey nations, children begin playing organised ice hockey from ages four to six. This means cumulative head impact exposure begins years or even decades before the brain is fully developed. The developing brain is more vulnerable to repeated impacts, and the earlier exposure begins, the longer the cumulative timeline.
Sub-concussive events: the silent, accumulating risk
Here is where the story of brain injury in ice hockey becomes most important – and most urgent.
A concussion is a diagnosable event. Something happened, symptoms appeared, and medical attention was sought. Sub-concussive events are different: they are the hundreds or thousands of head acceleration events across a season and career that are individually below the threshold for any clinical symptom. The player feels nothing. They continue. No one records it. And yet the evidence now clearly shows that these events are doing real and measurable damage.
The landmark 2024 Boston University study
The most significant piece of research on long-term brain health in ice hockey was published in December 2024 in JAMA Network Open by the Boston University CTE Centre – the largest study of its kind ever conducted on ice hockey players. The study examined the donated brains of 77 deceased male ice hockey players ranging from youth level to the National Hockey League. The findings were stark: The odds of having chronic traumatic encephalopathy (CTE) increased among hockey players by 34% for each year played. Of the professional players studied, 96% – including 18 of 19 NHL players – had CTE. Among those who had only played youth or high school hockey, the figure was 10%. These results make ice hockey the third major sport, after American football and rugby, to show a dose-response relationship between years of play and the risk of developing CTE.
The researchers were clear about what the dose-response relationship implies: it is not a single catastrophic concussion that drives CTE risk. It is cumulative exposure – the accumulation of impacts over time. Years of play is a proxy for these impacts that are harder to measure directly, but are likely what are leading to the disease.
Crucially, the study also found no CTE in any hockey player who had spent fewer than six years competing. The risk appears to be genuinely cumulative – it builds across time and exposure, not from any single event.
Brain changes in players with no concussion diagnosis
A study published in Brain Communications investigated sub-concussive brain changes in Bantam (under 14) and Junior-A (ages 16-20) male ice hockey players across a single season. None of the players were diagnosed with a concussion during the season.
The researchers found significant pre-to-post-season differences in brain vital signs in both groups, with a significant linear relationship between changes in brain vital signs and the total number of head impacts received during the season. In plain terms: even without a single concussion diagnosis, a season of ice hockey produced measurable neurological changes – and those changes were directly proportional to how many head impacts the player had experienced. Junior-A players averaged 195 head impacts across the season. Bantam players averaged 33. The neurological changes in Junior-A players were correspondingly greater.
Separately, research on collegiate ice hockey players using diffusion MRI found widespread changes in white matter microstructure between the start and end of a single competitive season – again in players with no concussion diagnosis during that season. Repetitive sub-concussive head impacts may lead to structural, functional, and metabolic alterations of the brain, and sex differences in these changes have also been observed, with male and female players showing different white matter response patterns to the same exposure.
What this means for how we think about brain safety in hockey
The combined picture from the research is clear and consistent: the brain changes associated with years of ice hockey play are not primarily the result of the concussions that get diagnosed and recorded. They are the result of the sustained, season-after-season accumulation of hundreds of impacts that never produced a symptom, never triggered a medical assessment, and were never counted.
This has profound implications for how brain safety in hockey is managed. If the primary risk is cumulative sub-concussive load rather than individual concussive events, then the tools that matter most are not just concussion protocols – though those remain essential – but the ability to track and manage the total head impact burden across a season, to identify players carrying unusually high loads, and to make data-informed decisions about training intensity, contact in practice, and load management across a playing career.
What the science says about prevention
The evidence on prevention in ice hockey is encouraging where action has been taken.
Removing checking from youth hockey reduces concussion rates at that level. Multiple studies have shown that leagues without body checking have lower concussion rates than those where it is permitted. The brain-development argument is particularly compelling: the developing brain is more vulnerable to rotational forces, and building checking skills before young players have developed adequate neck strength and anticipation may significantly increase risk.
However, rules address only part of the picture. Rule changes that reduce intentional contact do not address falls to the ice, collision events, puck and stick contact, or the sub-concussive load accumulated through body contact that is legal and normal within the game. They also do not address what happens in practice, where contact drills routinely generate head impacts in an environment with less formal oversight.
Load management in training is where the biggest gains may lie. If sub-concussive exposure accumulates most rapidly in training – where contact drills are repeated many times in controlled, measurable conditions – then managing contact loads in practice represents a practical, meaningful lever for reducing cumulative brain exposure across a season.
What coaches, clubs and players can do
Take the culture shift seriously. The idea that concussions are badges of toughness – part of what it means to play hockey – has to be replaced by an understanding that every significant head impact and event, diagnosed or not, contributes to cumulative load. This shift is happening at the elite level. It needs to reach grassroots hockey.
Apply the same removal-from-play standards at every level. Any player who shows signs of concussion – confusion, balance problems, appearing dazed, sensitivity to light, memory difficulties, or more – , or if is possible or suspected concussion may have occurred, Athlete must not return to play. This is non-negotiable at any age or level of competition.
Reduce high-contact repetitions in training. The most controllable source of cumulative brain load is practice. Drills involving repeated body contact can be designed to achieve their technical objectives with fewer high-intensity impact repetitions. Quality over quantity applies to contact training just as it does to heading repetitions in football.
Teach proper body contact technique. A player who knows how to absorb and deliver body contact with good positioning, with their head up and their neck braced, generates and receives lower rotational forces than one who is caught off-guard or in a vulnerable position. Technique training is protective.
Measure what is actually happening. This is where objective data becomes essential – and where the gap between what people believe is happening and what is actually happening can be largest. A head impact sensor worn in the headband during training and matches records every significant force event, providing coaches and team staff with objective data on the events occurring and cumulative brain load across the session and the season. Not to replace clinical concussion assessment, but to make the destructive forces and the sub-concussive burden visible and objectively measured, that until recently has been invisible and impossible to measure.
ACT Head Impact Tracker is used in elite women’s ice hockey in Finland’s Aurora Liiga, and the data it provides – number of impacts and events, magnitudes in them, frequency, and proximity of them – gives coaching and team staff the information needed to be aware and understand the events on the pitch when they are taking place, and measure, track and manage the brain load in ways that were simply not possible before.
The picture that is emerging
Ice hockey is a magnificent sport. Its demands of skill, physical courage, and teamwork are unique. The goal of brain safety research is not to diminish the sport but to give everyone who plays it the information and tools needed to manage the real risks it presents.
The December 2024 Boston University study makes the situation clear: the cumulative risk of brain disease in ice hockey is real, it increases with every year of play, and it affects players at all levels, not just the elite or the enforcers. The sub-concussive research shows that this risk builds across seasons in which no concussion is ever diagnosed. The neurological changes are happening anyway – silently and incrementally.
The response to this evidence has to be proportionate: better rules, better protocols, better culture, and better data. Making the invisible visible – turning the silent accumulation of forces on athletes’ brains into something that can be seen, objectively measured, tracked, and managed – is not a luxury for professional teams. It is the logical, necessary response to what the science now clearly shows.
There is no medication. No cure. Prevention – informed, consistent, and measurable – is the only path forward.
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