The Neurotrauma Dilemma: Culture, Biomechanics, and the Evolution of Safety in American Football

Abstract

Traumatic Brain Injury (TBI), particularly in the form of concussion and chronic neurodegenerative sequelae, represents the singular most significant existential, medical, and ethical challenge facing American football in the twenty-first century. From the Friday night rituals of high school athletics to the multi-billion-dollar spectacle of the National Football League (NFL), the sport is currently navigating a turbulent period of transition defined by a collision between entrenched cultural traditions and emerging neuropathological evidence. This report provides an exhaustive, multi-disciplinary examination of the current status of TBI in US football as of early 2026. It synthesizes epidemiological data from the 2024-2025 seasons, analyzes the shift from passive to active rehabilitation protocols, details the biomechanical revolution in protective equipment, and contrasts the resource-rich environment of professional leagues with the systemic disparities found in amateur athletics. By integrating recent findings on early-onset neuronal loss, blood-based biomarkers, and the efficacy of rule changes like the dynamic kickoff and hip-drop ban, this analysis illuminates the complex ecosystem of player safety.

I. Introduction: The Paradigm Shift in Gridiron Medicine

For the vast majority of American football’s history, the head injury was minimized, misunderstood, and mythologized. The vernacular of the sport—"getting your bell rung," "seeing stars," "shaking off the cobwebs"—served as a linguistic shield, diminishing a complex neurological event into a momentary lapse in fortitude. Players were routinely administered smelling salts and returned to the huddle, their disorientation viewed not as a symptom of brain trauma, but as a hurdle to be overcome by the "warrior mentality" that pervades the sport’s culture.

However, the last two decades have witnessed a seismic shift in this paradigm, driven by a convergence of high-profile litigation, advances in neuroimaging, and the grim discovery of Chronic Traumatic Encephalopathy (CTE) in the brains of deceased players. We have moved from an era of denial to an era of hyper-vigilance and data-driven intervention. In 2026, the management of TBI is no longer solely the domain of the sideline athletic trainer; it is a multidisciplinary effort involving neurotrauma consultants, engineers, legislators, and epidemiologists.

The scope of this crisis is vast. Millions of athletes participate in football across the United States, with the vast majority playing at the youth and high school levels. While the NFL captures the headlines with its elite medical resources and historic lows in concussion numbers—reporting a 17% decrease in the 2024 season ¹—the reality for the high school linebacker in a rural district is starkly different. This report aims to bridge the gap between these worlds, offering a detailed narrative of how the sport is attempting to engineer safety into a game predicated on violent collision.

II. The Pathophysiology of the Concussive Event

To understand the medical and engineering interventions currently in play, one must first possess a nuanced understanding of what occurs inside the skull during a football impact. A concussion is not merely a "bruise" to the brain, nor does it require the head to strike an object directly. Rather, it is a complex pathophysiological process induced by biomechanical forces.

The Neurometabolic Cascade

When a player sustains a significant impact—whether a direct blow to the helmet or a blow to the body that causes the head to snap back—the brain moves within the skull. This movement creates shear forces that stretch the cell membranes of neurons. This stretching disrupts the delicate balance of ions that normally allows nerve cells to fire.

In a healthy neuron, potassium is kept inside the cell and calcium and sodium are kept out. The mechanical force of a concussion creates "holes" or micropores in the membrane, leading to a massive, unregulated flux of ions. Potassium rushes out of the cell, while calcium and sodium rush in. This ionic shift triggers a "firestorm" of electrical activity, often manifested as the immediate fencing response (arms rigid in the air) or loss of consciousness seen in severe cases.³

To restore order, the brain's sodium-potassium pumps must work overtime, consuming vast amounts of adenosine triphosphate (ATP), the cell's energy currency. This creates a state of hypermetabolism—the brain is burning fuel at a frantic pace. However, in a cruel physiological twist, the concussion also causes a temporary constriction of blood vessels in the brain, reducing the supply of glucose and oxygen just when the demand is highest. This mismatch between supply and demand results in an "energy crisis" within the brain.

It is during this period of energy crisis that the brain is most vulnerable. If a second impact occurs before this metabolic balance is restored, the result can be catastrophic—a phenomenon known as Second Impact Syndrome, which, though rare, can lead to massive brain swelling and death, particularly in younger athletes whose brains are still developing.⁴

Beyond the Symptom: Sub-Concussive Impacts

While diagnosed concussions garner the most attention, the current state of the science has pivoted toward the accumulation of "sub-concussive" impacts. These are hits that do not result in immediate, observable clinical symptoms—the lineman blocking on every play, the running back being tackled without disorientation.

The "Iceberg Theory" of brain injury suggests that diagnosed concussions are merely the visible tip of a much larger problem. Recent research has validated this concern. A seminal study published in late 2025, funded by the NIH and conducted by researchers at Boston University, analyzed postmortem brain tissue from athletes under the age of 51. The findings were alarming: repetitive head impacts caused a striking 56% loss of a specific type of neuron in brain areas that typically absorb force, even in athletes who did not yet show the hallmark tau protein accumulation of CTE.⁵

This finding fundamentally changes the conversation. It implies that brain damage is not solely a binary outcome of "concussed" versus "not concussed," but a linear dose-response relationship to the total number of hits sustained over a career. This "hit count" hypothesis is now driving changes in practice regulations at all levels, as practice represents the single most controllable environment for reducing exposure.⁶

Chronic Traumatic Encephalopathy (CTE)

The long-term shadow over the sport remains CTE, a neurodegenerative disease characterized by the deposition of hyperphosphorylated tau protein in the sulci (grooves) of the brain. Historically associated with "punch drunk" boxers, CTE has been definitively linked to American football. The 2024 research landscape added a terrifying specificity to this risk: the risk of developing CTE doubles for every 2.6 years of football played.⁷

This statistic provides a grim calculus for parents and players. It suggests that a player who stops after high school faces a significantly different risk profile than one who plays through college and into the professional ranks. Furthermore, the 2025 NIH study showed that inflammation and microglial activation (the brain's immune response) occur years before the structural changes of CTE, suggesting a long window of "silent" disease progression that could potentially be targeted by future therapies.⁵

III. The Physics of the Hit: Biomechanics and Acceleration in Neurotrauma Etiology

The mechanism of injury in football is defined by two vectors: linear acceleration and rotational acceleration. Understanding the distinction between the two is critical to evaluating modern helmet technology and rule changes.

Linear vs. Rotational Acceleration

For decades, the standard for helmet safety was the drop test, which measured the helmet's ability to withstand a linear impact—a straight line force, like dropping a bowling ball on a floor. This focus was effective at virtually eliminating skull fractures and intracranial bleeds, which are typically caused by linear forces causing the brain to smash against the inner skull wall.⁸

However, the brain is viscoelastic, akin to a block of gelatin. It handles compression relatively well but handles shear forces poorly. Rotational acceleration—caused when the head is struck off-center or the body rotates while the head lags behind—causes the brain to twist inside the skull. This twisting stretches and tears axons (diffuse axonal injury), which is the primary driver of concussion symptoms and long-term degeneration.⁸

Recent biomechanical studies utilizing instrumented mouthguards (which couple tightly to the teeth and provide more accurate data than helmet sensors) have quantified these forces. A concussive impact in the NFL typically involves linear accelerations of around 98g and rotational accelerations exceeding 6,000 radians per second squared (rad/s²).⁸

Position-Specific Risks

The physics of the collision varies significantly by position, necessitating different protection strategies.

• Linemen: Experience the highest volume of impacts. These are typically lower velocity, sub-concussive hits occurring on nearly every play. Their risk profile is driven by the cumulative load (the "hit count").

• Wide Receivers and Defensive Backs: Experience fewer impacts, but of much higher magnitude. These players are often running at full speed in open space. When a collision occurs, the change in velocity (delta-V) is massive, leading to high linear and rotational spikes. The 2024-2025 data indicates that wide receivers remain the most concussion-prone position group in college football due to this "tunnel vision" exposure while tracking the ball.¹⁰

• Quarterbacks: Vulnerable to "whiplash" impacts where they are sacked from the blind side, causing rapid head rotation even without direct helmet contact.

Table 1: Comparative Epidemiology of TBI Across Levels

Metric	Youth Football (Ages 9-14)	High School Football	Collegiate Football (NCAA)	Professional Football (NFL)
Concussion Rate	Moderate; higher in games than practice.	Highest rate per athletic exposure (approx. 11.2 per 10,000).11	High; Competition rate ~10x higher than practice.12	Lower incidence rate due to elite prevention; 17% drop in 2024.1
Primary Mechanism	Poor tackling technique; weak neck musculature.	Variation in skill; speed disparity.	High-velocity collisions; targeting.	Extreme velocity; complex blocking schemes.
Practice vs. Game	Practice impacts significantly reduced by rules.6	Practice risk reduced, game intensity high.	High intensity in games; controlled practice contact.	Highest velocity collisions in games; highly regulated practices.
Reporting Culture	Barriers due to fear of removal/lack of knowledge.13	High pressure to play; "sandbagging" baselines common.	Improved reporting but scholarship pressure exists.	Strict "No-Go" signs; independent spotters.

IV. The Engineering of Safety: Equipment Innovation

In response to the biomechanical reality of rotational forces, the equipment industry has undergone a revolution. The era of the polycarbonate shell lined with simple vinyl nitrile foam—a design that remained largely unchanged from the 1970s to the 2000s—is over.

The Decoupling of the Shell

The central innovation in modern helmet design is the decoupling of the outer shell from the inner liner to manage rotational energy.

• MIPS (Multi-directional Impact Protection System): Originated in Sweden, this technology inserts a low-friction layer between the helmet's padding and the head. Upon impact, the helmet slides 10-15mm relative to the head, redirecting rotational energy that would otherwise be transmitted to the brain.¹⁴ While widely adopted in cycling and snow sports, its efficacy in football is debated, with some independent testing suggesting that the scalp itself acts as a natural slip plane, diminishing the added value of the MIPS layer in certain impact scenarios.¹⁶

• Deformable Shells (VICIS): The VICIS Zero1 and Zero2 helmets radically departed from tradition by using a soft, deformable outer shell that yields like a car bumper upon impact. Beneath this shell, columns of flexible structures buckle to absorb both linear and rotational loads.¹⁷ This design increases the duration of the impact event, thereby lowering the peak acceleration transferred to the head.

• Tectonic Plates (Schutt): Manufacturers like Schutt have introduced helmets with independent panels on the exterior (the F7 model) that move three-dimensionally to disperse energy, mimicking the movement of tectonic plates.¹⁷

The Rise of the Guardian Cap

The most visible and controversial equipment change in the 2024-2025 seasons was the widespread adoption of the Guardian Cap. This soft-shell polyurethane cover snaps over the traditional hard-shell helmet, effectively giving the player a "helmet for their helmet."

The theory is simple: physics dictates that a softer surface increases the time duration of an impact, which reduces the peak force. The NFL's internal data was compelling. The league reported a 52% reduction in concussions for position groups mandated to wear the caps during training camps.¹⁸ Based on this success, the NFL permitted players to wear Guardian Caps during regular-season games for the first time in 2024. While aesthetically jarring to purists, the adoption by 20 players in live games contributed to the league's overall concussion reduction.¹

However, the Guardian Cap is not without detractors. A 2025 study from the University of Miami challenged the cap's real-world effectiveness in the collegiate setting. Tracking 54 college players over a season, researchers found no significant difference in head impact magnitude or frequency between those wearing the caps and those without.¹⁹ This discrepancy—effective in the NFL, questionable in college—may boil down to impact types. The caps are most effective at dampening the sub-concussive, low-velocity blows common in practice (linemen banging heads) rather than the high-velocity, open-field collisions seen in games. Additionally, the "risk compensation" theory suggests that players wearing extra protection may unconsciously play more aggressively, negating the safety benefit.¹⁹

Economic Disparities in Equipment

A critical ethical dimension of equipment safety is cost. An NFL player takes the field in a custom-fitted, laboratory-tested helmet often costing over $1,000, supplanted by a Guardian Cap. In contrast, high school budgets are finite. A rural high school football program may be equipping players with reconditioned helmets that are several years old.

Research into cost-effectiveness has become vital for high school athletic directors. Virginia Tech’s "STAR" rating system has democratized safety data, allowing schools to identify mid-range helmets (like the Schutt Vengeance Z10) that offer protection comparable to elite models at a fraction of the price.²⁰ Nonetheless, the gap remains: the highest level of safety technology is often a luxury good, leaving amateur athletes—who are statistically more prone to injury due to poor technique—with inferior protection.

V. Medical Management: Diagnosis and Protocols

The medical management of concussion has transitioned from a subjective art to an objective, protocol-driven science. This section details the current standards of care, highlighting the differences between professional and amateur levels.

The NFL Concussion Protocol (2025)

The NFL's protocol is the gold standard for resource-intensive management. It is a rigorous, multi-step process designed to remove the player's volition from the decision-making loop.

1. Identification and the "Eye in the Sky": The protocol utilizes "Booth ATC Spotters" and "Unaffiliated Neurotrauma Consultants" (UNCs) who monitor video feeds from the stadium press box. They have the power to call a "Medical Timeout" to stop the game if they observe a player exhibiting signs of distress.³

2. The "No-Go" Signs: Specific observable behaviors result in immediate, permanent removal from the game. These include:

3. Loss of Consciousness (LOC).

4. Ataxia (gross motor instability, stumbling).

5. Confusion.

6. Amnesia.

7. The "Fencing Response" (involuntary arm extension).

8. Impact Seizure. If any of these are observed, the player is ineligible to return, regardless of their performance on subsequent tests.³

9. Sideline Assessment: If a player is suspected of a concussion but does not show "No-Go" signs, they undergo a sideline survey. This includes the Maddocks questions ("What quarter is it?", "Who did we play last week?") and a focused neurological exam.

10. Locker Room Evaluation: If the sideline assessment is suspicious, the player is taken to the locker room for the full NFL Locker Room Comprehensive Concussion Assessment, which includes the SCAT6 (Sport Concussion Assessment Tool, 6th Edition) and comparison to their preseason baseline.³

The Biomarker Revolution: Abbott i-STAT

A major limitation of concussion diagnosis has always been its reliance on subjective symptoms. Players can lie about headaches; they cannot lie about their blood chemistry.

In 2024 and 2025, the landscape changed with the FDA clearance and wider adoption of the Abbott i-STAT TBI test. This handheld device, using a whole blood sample, can produce results in 15 minutes right at the bedside or sideline.²² It measures two biomarkers:

• UCH-L1 (Ubiquitin C-terminal Hydrolase L1): A protein indicative of neuronal cell body injury.

• GFAP (Glial Fibrillary Acidic Protein): A marker of astrocytic (glial cell) injury.

While currently approved primarily to rule out the need for a CT scan (i.e., to detect intracranial bleeds), its utility in diagnosing mTBI is the frontier of sports medicine. High negative predictive value means that if the test is negative, the medical staff can be 99% sure there is no bleed. As specificity improves, this tool is expected to become the definitive "red light" for concussion removal.²³

Disparities in Junior Levels

While the NFL has Booth Spotters and blood tests, high school and college protocols vary wildly based on resources.

• NCAA: The NCAA mandates a Concussion Safety Protocol Checklist. This requires "Independent Medical Care," giving team doctors unchallengeable authority over coaches. It also mandates baseline testing and the presence of medical personnel at all contact games.²⁵ However, the 2024 season showed that while protocols are strong on paper, the pressure to return star athletes remains a powerful cultural force.

• High School: The disparity here is profound. A 2015 study (which remains structurally relevant) highlighted that many public high schools, facing budget cuts, are forced to choose between hiring teachers or Athletic Trainers (ATs). Consequently, nearly a third of US high schools lack full-time access to an AT.²⁶ In these schools, the diagnosis of a brain injury falls to a coach who may only have basic first-aid certification. This creates a dangerous conflict of interest and a lack of medical competency on the sideline.

VI. Rehabilitation: From the Dark Room to the Treadmill

Perhaps the most significant clinical reversal in the last decade is the treatment of the concussed athlete. For years, the standard of care was "cocoon therapy"—strict rest in a dark room, no screens, no reading, and no school until symptoms resolved. We now know this was wrong.

The Shift to Active Rehabilitation

Research led by the University of Buffalo and others has demonstrated that prolonged rest can actually delay recovery by inducing physical deconditioning and anxiety. The current standard, as of 2025, is "Active Rehabilitation."

• The Buffalo Concussion Treadmill Test (BCTT): This protocol involves putting a symptomatic patient on a treadmill and gradually increasing the incline/speed until their symptoms exacerbate. The heart rate at which symptoms increase is the "Heart Rate Threshold."

• Prescription: The patient is then prescribed aerobic exercise at 80-90% of that threshold. This sub-symptom exercise improves autonomic nervous system regulation (fixing the blood flow issues caused by the concussion) and releases Brain-Derived Neurotrophic Factor (BDNF), which aids in repair.²⁸

• Timeline: Guidelines now suggest reintroducing light activity as soon as 24-48 hours post-injury.⁴

Vestibular and Ocular Therapy (VOMS)

Many concussions result in vestibular (balance) and ocular (vision) dysfunction. Patients may feel dizzy when turning their heads or have trouble focusing. Vestibular rehabilitation involves specific exercises to retrain the brain's ability to integrate vision and inner-ear signals. Research on youth athletes in 2025 showed that individualized exercise prescriptions for gaze stability significantly improved outcomes compared to rest alone.²⁹

Return-to-Learn (RTL)

For the student-athlete, the "student" part requires medical management too. The NFL player does not have to take a calculus exam while their brain is in an energy crisis; the high school junior does.

"Return-to-Learn" protocols are now a mandatory precursor to "Return-to-Play." These involve academic accommodations such as:

• Shortened school days.

• No standardized testing.

• Printed notes (to avoid screen time).

• Sunglasses in class (for light sensitivity).

A narrative case study highlights the importance of this: a 15-year-old athlete suffering from post-concussive headaches found that cognitive exertion (math homework) triggered symptoms just as much as physical exertion. Her recovery required a graduated return to the classroom before she was ever cleared to return to the field.³¹

VII. The Regulatory Landscape: Changing the Rules

If medicine handles the injury and engineering softens the blow, the rules of the game attempt to prevent the collision entirely.

The Hip-Drop Ban and Dynamic Kickoff

The 2024 NFL season introduced two radical changes aimed at safety:

1. The Dynamic Kickoff: The kickoff has historically been the most dangerous play in football due to the high speed of players running 40 yards before colliding. The new rule aligns the coverage and return teams only 5 yards apart, eliminating the running start. This reduces the kinetic energy of the impact significantly.³²

2. The Hip-Drop Tackle Ban: The league banned the "swivel hip-drop tackle," where a defender wraps a runner and uses their dead weight to drop onto the runner's legs. While primarily aimed at high ankle sprains, this chaotic tackling style often results in whiplash-like head trauma. The ban was controversial among defenders but contributed to the historic low in injuries.³³

Targeting: NCAA vs. NFL

A major divergence exists in how the leagues punish dangerous hits.

• NCAA (Strict Liability): In college, the "Targeting" rule is draconian. If a player makes forcible contact with the crown of the helmet or strikes a defenseless player in the head/neck, it is a 15-yard penalty and an automatic ejection. The player is removed from the game immediately. This has created a culture of fear around high hits, forcing a change in tackling technique.³⁵

• NFL (Discretionary): The NFL penalizes similar hits as "Unnecessary Roughness" (15 yards). While fines are levied post-game, on-field ejections are rare and reserved for only the most egregious, flagrant acts. Critics argue the NFL's refusal to adopt the automatic ejection rule undermines its safety messaging.

Table 2: Regulatory and Rule Differences (2025)

Rule/Regulation	NFL (Professional)	NCAA (College)	NFHS (High School)
Kickoff Format	Dynamic Kickoff: Players aligned 5 yards apart; static start for coverage.	Touchback on fair catch inside 25 yields ball at 25. Standard alignment.	Standard kickoff; touchback places ball at 20.
Targeting Penalty	15 yards; fine; ejection rare (discretionary).	15 yards; Automatic Ejection (Strict Liability).	15 yards; Ejection for flagrant acts only.
Practice Contact	Severely limited padded practices; Guardian Caps mandated.	Limited full-contact days; strictly monitored.	State-by-state variations; generally limited. Focus on "Hit Count."
Defenseless Player	Extensive definition; strict protection of QBs and receivers.	Similar to NFL; emphasis on head/neck area.	Strong emphasis; prohibits "slapping" head.37

VIII. Disparities and Culture at the Junior Levels

The narrative of football safety is often a tale of two cities: the highly protected professional ecosystem and the precarious world of youth sports.

The Reporting Barrier

Despite increased education, the culture of silence persists. A qualitative study of high school athletes revealed that "knowledge" of concussion symptoms did not translate to "reporting" behavior. Athletes understood the risks (even death) but cited fear of removal from the game, letting down teammates, and the ambiguity of symptoms as reasons to stay quiet.¹³ This "warrior culture" is reinforced by parents and coaches who may resist the diagnosis to keep a star player on the field.³⁸

The Access Gap

The most profound failure in the system is the lack of medical equity. The "Hawaii Model"—where every public high school is required to have an athletic trainer—remains an anomaly. In many states, the presence of an AT is a luxury of affluent suburban districts. In rural or inner-city schools, the "medical staff" is often a coach with a cooler of ice. This disparity means that the athletes most in need of protection—those with developing brains, inferior equipment, and less skilled coaching—are often the ones with the least medical oversight.²⁶

IX. Conclusion: The Future of the Game

As we look toward the 2026 season and beyond, the status of Traumatic Brain Injury in US football is a paradox of immense progress and persistent peril.

We have successfully engineered a safer game for the professional. The 2024 NFL data—a 17% drop in concussions to historic lows—validates the strategy of rule changes (Dynamic Kickoff), equipment mandates (Guardian Caps), and rigorous protocols.¹ The "League of Denial" is dead; the NFL is now a league of data.

However, the democratization of this safety remains the sport's greatest challenge. The high school quarterback in a budget-strapped district plays a different game than the NFL star. He faces higher risks with older equipment, lacks the safety net of a sideline neurotrauma consultant, and relies on a support system that may prioritize winning over wellness.

The science has also delivered a sobering warning: the danger is not just the "big hit," but the thousands of silent, sub-concussive blows that slowly erode the brain's reserve. The 2025 NIH findings on early neuronal loss serve as a stark reminder that we cannot engineer our way out of human biology completely.⁵

The future of football depends on its ability to trickle down the protections of the NFL to the grassroots level. It requires universal mandates for athletic trainers, strict age limits on tackling to reduce lifetime exposure, and the continued evolution of diagnostic tools like blood biomarkers to take the guesswork out of safety. Until the Friday night lights shine on a field as safe as the Super Bowl, the work remains unfinished.

Technical Appendix: Statistical & Data Summary

A. 2024-2025 Injury Data Summary

• NFL Concussion Reduction: 17% decrease overall (2024 vs 2023).

• NFL Guardian Cap Efficacy: 52% reduction in concussions for mandated position groups (Training Camp data).

• High School Concussion Rate: ~11.2 per 10,000 athletic exposures (Highest among all sports).

• College Concussion Rate: Competition rate is ~10x higher than practice rate.

B. Diagnostic Tool Comparison

Tool	Type	Mechanism	Utility
SCAT6	Clinical	Symptom checklist, balance, memory, neuro exam.	Standard of care for diagnosis. Subjective elements.
ImPACT	Neurocognitive	Computerized test of reaction time, memory, processing speed.	Best used for baseline comparison during recovery.
Abbott i-STAT	Biomarker	Blood test for UCH-L1 and GFAP proteins.	FDA Cleared. High negative predictive value to rule out bleeds.
VOMS	Vestibular	Tests eye movement, convergence, and motion sensitivity.	Identifies vestibular dysfunction often missed by SCAT.
Buffalo Treadmill	Exertional	Graded exercise test to find heart rate threshold.	Gold standard for prescribing active rehabilitation.

C. Glossary of Key Terms

• Ataxia: Loss of control of body movements; stumbling or staggering. A "No-Go" sign in the NFL.

• Coup-Contrecoup: A pattern of injury where the brain strikes the skull on the side of impact (coup) and then rebounds to strike the opposite side (contrecoup).

• Diffuse Axonal Injury (DAI): Widespread tearing of nerve fibers (axons) caused by rotational shearing forces.

• Second Impact Syndrome: Rapid, often fatal brain swelling that occurs when a second concussion is sustained before the first has healed.

• Tau Protein: A protein that stabilizes microtubules in neurons. In CTE, it becomes hyperphosphorylated and forms tangles, destroying brain cells.

Works cited

1. Concussions Decrease to Historic Low in 2024 NFL Season, accessed February 7, 2026, https://operations.nfl.com/updates/football-ops/concussions-decrease-to-historic-low-in-2024-nfl-season/

2. 2024 NFL Data with Guardian Caps - Guardian Sports, accessed February 7, 2026, https://guardiansports.com/2025/02/07/nfl-data-2024-season/

3. NFL Head, Neck and Spine Committee's Concussion ... - NFL.com, accessed February 7, 2026, https://static.www.nfl.com/image/upload/v1758892132/league/qjqlkfe9ffaivuugiqcf.pdf

4. Following Return-to-Play Guidelines Essential in Concussion Recovery - NFHS, accessed February 7, 2026, https://nfhs.org/stories/following-return-to-play-guidelines-essential-in-concussion-recovery

5. Repeated Head Impacts Cause Early Neuron Loss, Inflammation in ..., accessed February 7, 2026, https://nihrecord.nih.gov/2025/12/05/repeated-head-impacts-cause-early-neuron-loss-inflammation-young-athletes

6. Comparing Head Impacts in Youth Tackle and Flag Football | Traumatic Brain Injury & Concussion | CDC, accessed February 7, 2026, https://www.cdc.gov/traumatic-brain-injury/data-research/comparing-head-impacts/index.html

7. Understanding CTE: The Hidden Risk in Football and How SAFR Is Working to Prevent It, accessed February 7, 2026, https://safrsports.com/2025/05/understanding-cte-the-hidden-risk-in-football-and-how-safr-is-working-to-prevent-it/

8. Biomechanical Perspectives on Concussion in Sport - PMC, accessed February 7, 2026, https://pmc.ncbi.nlm.nih.gov/articles/PMC4975525/

9. How Does Rotational Force Cause Brain Injury in Sport and How Can It Be Reduced?, accessed February 7, 2026, https://www.rezonwear.com/insights/rotational-force/

10. Prevalence of Concussions by Positions in ... - Liberty University, accessed February 7, 2026, https://digitalcommons.liberty.edu/cgi/viewcontent.cgi?article=2822&context=research_symp

11. [Study] Concussions and High School Athletes | Aguirre Law Firm, accessed February 7, 2026, https://www.aguirrelawpllc.com/blog/2023/05/study-sports-related-concussions-among-high-school-athletes/

12. 2023/24 National High School Sports-Related Injury Surveillance Study Prepared for the NFHS by Dr. Chris - MSHSAA, accessed February 7, 2026, https://www.mshsaa.org/resources/SportsMedicine/2023-24%20NFHS%20ISS%20Summary%20Report%20-%20August%202024%20-%20FINAL.pdf

13. Qualitative study of barriers to concussive symptom reporting in high school athletics - PubMed, accessed February 7, 2026, https://pubmed.ncbi.nlm.nih.gov/23427783/

14. Helmet technology - How it works - Mips, accessed February 7, 2026, https://mipsprotection.com/helmet-technology/

15. Rotational motion - Mips AB, accessed February 7, 2026, https://mipscorp.com/about-mips/rotational-motion/

16. MIPS and Sliding Resistance of Bicycle Helmets, accessed February 7, 2026, https://helmets.org/mips.htm

17. A football helmet prototype that reduces linear and rotational ... - NIH, accessed February 7, 2026, https://pmc.ncbi.nlm.nih.gov/articles/PMC6289811/

18. Guardian Caps | Secure Support from Boards, Boosters and Donors, accessed February 7, 2026, https://guardiansports.com/2025/07/24/secure-support-from-boards-and-donors/

19. KSS Research Challenges Guardian Cap Effectiveness in College Football, accessed February 7, 2026, https://news.miami.edu/edu/stories/2025/12/kss-research-challenges-guardian-cap.html

20. A Cost-Effective Analysis of Modern Football Helmets at the High School Level - Scholar Commons, accessed February 7, 2026, https://scholarcommons.sc.edu/cgi/viewcontent.cgi?article=1624&context=senior_theses

21. Choosing the Right Helmet for You - Guardian Sports, accessed February 7, 2026, https://guardiansports.com/2025/08/07/choosing-the-right-football-helmet/

22. Abbott Receives FDA Clearance for Whole Blood Rapid Test to Help with Assessment of Concussion at the Patient's Bedside, accessed February 7, 2026, https://abbott.mediaroom.com/2024-04-01-Abbott-Receives-FDA-Clearance-for-Whole-Blood-Rapid-Test-to-Help-with-Assessment-of-Concussion-at-the-Patients-Bedside

23. FDA Clears Abbott's i-STAT Traumatic Brain Injury Whole Blood Test as Bedside Assessment | NeurologyLive, accessed February 7, 2026, https://www.neurologylive.com/view/fda-clears-abbott-i-stat-traumatic-brain-injury-whole-blood-test-bedside-assessment

24. Biomarker-Based Point-of-Care Tests for the Evaluation of Mild Traumatic Brain Injury | CDA-AMC, accessed February 7, 2026, https://www.cda-amc.ca/biomarker-based-point-care-tests-evaluation-mild-traumatic-brain-injury

25. Concussion Safety Protocol Checklist, accessed February 7, 2026, https://ncaaorg.s3.amazonaws.com/ssi/concussion/2020_Concussion_Safety_Protocol_Checklist.pdf

26. Athletic Directors' Barriers to Hiring Athletic Trainers in High Schools ..., accessed February 7, 2026, https://pmc.ncbi.nlm.nih.gov/articles/PMC4641544/

27. Athletic Training Settings: Secondary School vs. Collegiate | MUSC, accessed February 7, 2026, https://www.musc.edu/content-hub/News/2022/06/16/Athletic-Training-Settings

28. NEJM Paper: Active Management Most Effective Concussion Treatment, accessed February 7, 2026, https://medicine.buffalo.edu/news_and_events/news/2025/1/leddy-nejm-paper-concussion-21791.html

29. Exploring New Frontiers in Concussion Rehabilitation in: Journal of ..., accessed February 7, 2026, https://journals.humankinetics.com/view/journals/jsr/34/3/article-p191.xml

30. Active Recovery for Concussions | Patient Education - UCSF Health, accessed February 7, 2026, https://www.ucsfhealth.org/education/active-recovery-concussion

31. Case Study: High School Sports Concussions - Info on Medical Treatment Algorithms, accessed February 7, 2026, https://blog.medicalalgorithms.com/high-school-sports-concussions/

32. Concussions decrease to historic low in 2024 NFL season, accessed February 7, 2026, https://www.nfl.com/news/concussions-decrease-historic-low-2024-dynamic-kickoff-lex-hip-drop-tackle

33. 2024 NFL rule changes: Kickoffs, hip-drop tackles and instant replay | FOX Sports, accessed February 7, 2026, https://www.foxsports.com/stories/nfl/how-kickoffs-will-look-different-2024-other-rule-changes-coming-nfl

34. NFL Approves Three Rule Changes For 2024 - Seattle Seahawks, accessed February 7, 2026, https://www.seahawks.com/news/nfl-approves-three-rule-changes-for-2024

35. Why is targeting not a penalty in the NFL the way it is in college? : r/NFLNoobs - Reddit, accessed February 7, 2026, https://www.reddit.com/r/NFLNoobs/comments/1nrho01/why_is_targeting_not_a_penalty_in_the_nfl_the_way/

36. NFHS vs Collegiate Comparison Chart 2025 - USA Lacrosse, accessed February 7, 2026, https://www.usalacrosse.com/sites/default/files/documents/Rules/2025-NFHSvsCollegiate-Comparison-Chart.pdf

37. Prohibition on Slapping the Head Now Applies to All Players in High School Football - NFHS, accessed February 7, 2026, https://nfhs.org/stories/prohibition-on-slapping-the-head-now-applies-to-all-players-in-high-school-football

38. Study Finds High Schools Had Challenges Enforcing Concussion Protocols, accessed February 7, 2026, https://www.wosu.org/news/2019-11-22/study-finds-high-schools-had-challenges-enforcing-concussion-protocols