MECHANISTIC INSIGHTS INTO SPORT-RELATED CONCUSSION: ACCELERATION/DECELERATION OF THE BRAIN

PROLOGUE

For years and years, we have been trying to come up with a better way to protect our brain. God did not design our brains without protection! He gave us a bony skull so that there would never be any impact that would directly contact our brain. We as humans have provided assistance with this design by adding another layer of protection via a helmet to assist in this part of God's design to protect the brain. This layer of protection further ensures that the skull will not fracture, and direct contact cannot occur to the brain risking catastrophic injury. In our present age, the NFL and helmet companies have the labeled this HeadHealth Technology. And all their resources go into trying to create a better helmet. And since they control the narrative and paradigm of thought, we believe this is the only way to protect the brain. So much so we continue to make larger and heavier helmets which can add to the increased risk of brain injury after impacts.

God has also designed the structural anatomy of our brain within the skull to protect itself from injury. And I am here to tell you the brain does not bounce back and forth after impact, or float in fluid, or slosh around inside the skull. The brain does not move in a wave, and it is never trying to catch up to the skull. These theories of brain movement within the skull do not match with God's structural design of our brain.

In August of 2020 I read that VICIS, the helmet that was going to save football and drastically reduce the occurrence and severity of concussion in football sold to Schutt for 2.85 million after spending 90 million. At that time, I had received reports from parents about how effective Kato Collar worked in protecting their son from concussion. My first thought was, "Why is Kato Collar working so well and VICIS basically went out of business?"

I believed I knew why we were working, but I felt I needed to be able to justify that truth about how and why Kato Collar was working to protect against concussion. The one thing I did know was truth, is that all our theories behind how the brain was injured from impacts were simply that, "A Theory". Why? Because to my knowledge we do not yet have the technology to put a camera inside the skull to clearly image or view how a brain moves inside a skull upon impact and after impact. As a result, I began investigating and researching the anatomy of the brain, mechanism of injury, and helmet testing, regarding sport related concussion (SRC) in football.

The one thing I have determined from my research is that most experts believe it is acceleration and deceleration of the brain that causes SRC in football. The question then becomes, "How and when does the brain accelerate and decelerate in relation to head/helmet acceleration and deceleration?". From my research I came to the following simple conclusions. And I am writing them at the beginning so that you will read the following paper to see how I came to those conclusions. (More in-depth conclusions will be included at the end of this paper.)

1. The brain does not accelerate or decelerate on its own.
2. The brain does not decelerate or accelerate at the same time that the head/helmet does.
3. There is never direct contact to the brain at the time of a direct impact to the head/helmet or an indirect impact to the body.
4. The brain is pushed back and forth within the skull after all impacts.
5. Helmets only protect the head/skull upon direct impact and therefore MAY indirectly provide protection for the brain.
6. Helmets can only protect the head/skull at the impact location (IMPL).
7. Helmets can only protect the head/skull during the time period of the impact.
8. The reason behind the design of helmets has changed over time.
9. Heavier helmets increase the risk of SRC after impacts.
10. New protective equipment needs to be designed that works with the helmet and shoulder pads to slow down the head/helmet after impact to provide a safety system which addresses more of the mechanisms causing SRC.

INTRODUCTION

What is the truth about sport-related concussion (SRC) in contact sports? The narrative and paradigm of the mechanism of injury (MOI) to the brain we have been taught is not the complete truth. And it begins with what we have been taught throughout our lives in the classroom and what has been told to us through the media about SRC . When you think about the brain and the picture created in your mind by what you have been taught in anatomy courses and by what you have seen and read, what do you see? (Fig. 1)

Figure 1. Structures of the Brain

Answer, the structural anatomy of the brain. The cerebrum, cerebellum, brain stem, and so on. The problem is that there are other structures of the brain which have not been included in that picture. (Fig. 2 & 3.)

Figure 2. Meninges        Figure 3. CSF and Ventricular System

If you only see the brain as it is in Figure 1 which is what we have been led to believe through our education and media, you could be convinced that the only way to protect against the forces that cause concussion (brain injury) would be to reduce the forces that act on the skull from a direct hit to the head through absorption upon direct contact via a helmet. And this narrative has been promulgated by football helmet companies and the NFL via the NFL-NFLPA Helmet Testing Performance Results over the last 10 years. Millions of dollars have been spent over the past decade on improvement of helmets in football and yet helmet manufacturers have not found the answer to reduce concussion. If they had, then why is the NFL and UFL requiring players during training camps to wear additional protection to add additional absorption on contact. Yet, they promote that they are making the game safer through science. If this is the case and the NFL and helmet companies are improving, there are two questions which need to be answered: 1) Why is there only a ranking of helmets in a chart that are approved without any data or science behind it showing why one helmet may be better than another helmet? [1,2,3,4,5] ; and 2) What are the kinematic measures being used to collect the scientific data demonstrating improvement in helmets?

The number one truth behind the MOI to the brain causing SRC is based on theory. And what is tested is based on theory. Leading us to believe throughout the years that absorption on contact which only a helmet can provide is the only way to prevent SRC. The problem with this is that no one knows exactly how the brain moves within the skull, and until we can put a camera inside the skull to visualize and measure that movement, everything being presented to us is theory. To my knowledge, at this time, that technology does not exist.

The goal of this paper is to present to you a new theory of brain movement resulting from direct and indirect contact, and how we must go beyond just a helmet to better protect the brain from injury. This theory is based on God's design of our structural anatomy of the head, neck, and brain, and the laws of science as we know them to exist currently. This paper is based on research of our structural anatomy of the brain, MOI, helmet testing relating to prevention, brain movement related to impact and after impact. And in conclusion, with why and how we need to start innovating beyond just the helmet to prevent SRC.

SPORTS RELATED CONCUSSION (SRC)

Concussion has been defined in many ways. Concussion is a type of mild traumatic brain injury"”or MTBI"”caused by a bump, blow, or jolt to the head (direct impact) or by a hit to the body (indirect impact) that causes the head to move rapidly back and forth and therefore, the brain to move rapidly back and forth. This impact to the head or body leads to problems with thinking or other neurological symptoms. Although a concussion occurs with the same mechanism in sports as it does in any other activity, sport-related concussion (SRC) has been used to describe any concussion that occurs while participating in sport. We have been presented with many different theories that an impact to the head or body causing the head to move violently in turn causes the brain to bounce around smashing into the inside of the skull causing SRC.

Throughout the years these theories have described the brain as bouncing, floating, sloshing, shaking, moving in a wave, and now we even have experts describing the motion of the brain from impacts as "lagging behind and trying to catch up to the skull". [6] Through this video from the CDC website we are moved to believe that the brain lags behind, then the brain catches up and smashes into the skull. It rebounds off the skull and then proceeds to run into the other side of the skull. https://www.cdc.gov/headsup/basics/concussion_whatis.html [7] This is similar to what was depicted in the movie "Concussion" when they showed the tennis ball bouncing back and forth in its cannister. Most of the experts now agree that acceleration/deceleration of the brain inside the skull is what causes SRC. How this occurs is still unknown. Since we know already know that a SRC can only occur from a direct or indirect impact causing the head to move violently, the only conclusion left is that acceleration/deceleration of the brain can only occur when the head and neck is accelerated or decelerated beyond their ability to protect the brain and/or the brain's ability to absorb its own forces. As a result of this conclusion, we have made the assumption that upon impact to the head, force is elicited to the brain causing it to move away from the inside of the skull. But based on the structural anatomy of the brain this does not occur. To be able to understand this we must begin with a review of the structural anatomy of the brain and how God designed our brain to absorb its own forces.

HEAD, NECK, and BRAIN ANATOMY

The Head and Neck: In human anatomy, the upper portion of the body consisting of the skull with its coverings and contents, including the lower jaw is defined as the head. The skull is attached to the spinal column via the first cervical vertebrae called the atlas. [8] The head is connected to the trunk of the body and moved by muscles of the head and neck through the motions of cervical flexion, extension, lateral flexion, and rotation. [9] Figures 4 & 5 depict this anatomy.

Figure 4. Bony anatomy of skull

Figure 5. Non bony anatomy of the head and neck

The Skull: When discussing SRC it is important to note that the hair, scalp, periosteum, and bone of the skull are not in any way attached to the brain. Everything below the bony portion of the skull is part of the brain (Figure 6). The scalp and cranial bones provide mechanical protection to the brain. [10] When talking about helmets and absorption of energy upon impact from the helmet we must consider the skull as part of the protection of the brain. It is there to prevent any direct contact with the brain. NOTE: This is why refer to the head and helmet as one entity "“ head/helmet. As the helmet is there to prevent any direct contact to the head/skull.

Figure 6. Relationship of the Skull to the Brain

The Brain: Typically, when we are introduced to the brain in anatomy, we see a picture as above in Figure 1 or below in Figure 7.

Figure 7. Side View of the Brain

The problem with these images is that they are truly only showing us some of the structures (parts) that make up the brain. The brain includes all structures below the skull and are contained within the skull. This includes the linings, spaces, ventricles, cerebrospinal fluid (CSF), the four major regions and everything that make up the brain. Note that in Figure 6 the line pointing to the brain is pointing to the cerebrum. Figures 1 and 7 show us the four major regions of the brain. The four major regions of the brain are the cerebrum, cerebellum, diencephalon, and brain stem. The average weight of the human brain is approximately 3 to 3.3 pounds. [11, 12] Through these images of Figures 1 and 7 we have been ingrained with a paradigm that the structures which make up the brain are what constitute the entire brain. The problem is that there is no inclusion of the dura mater, arachnoid mater, pia mater, and the spaces between which contain cerebrospinal fluid (CSF) and other structures of the brain. As a result, we are led to believe that the CSF is outside the brain next to the skull. And hence that the brain bounces, floats, or sloshes back and forth with any impact. If there is no CSF outside of the brain, then the brain is not bouncing or floating around inside the skull.

Structures of the Brain:

Cerebrum consists of two hemispheres and four lobes: frontal, temporal, parietal, and occipital (Fig. 1 and 7 above). [10] The cerebral cortex is the outermost layer of the brain of about 1.5 mm to 5mm of the cerebrum. It is covered by a meninges and is subcortical, made up primarily of grey matter. [13, 14] The falx cerebri is a sickle shaped fold of dura mater dividing the two cerebral hemispheres in the longitudinal fissure. [10] The cerebrum is the largest part of the brain, and its right and left hemispheres are joined by the corpus callosum. The cerebrum makes up approximately 85% of the brain's weight. [12, 15]

Cerebellum stands for "little brain" and is part of the brain and a structure of the central nervous system that is located at the back of the brain, underlying the occipital and temporal lobes of the cerebral cortex. (Fig. 7) Although the cerebellum accounts for approximately 10% of the brain's volume, it contains over 50% of the total number of neurons in the brain. [16] The weight of an adult human cerebellum is 150 grams. 150 grams is equivalent to 0.330693 pounds. This is approximately 10% of the brain's weight. [17]

Brainstem (Fig. 5 & 6) The brain stem consists of the diencephalon (thalamus and hypothalamus), midbrain (mesencephalon), pons, and medulla oblongata in descending order below the cerebrum. The brain stem and surrounded by the four cerebral lobes of each hemisphere. The medulla oblongata connects the brainstem to the spinal cord. [10]

Figure 8: Median view of brain

Figure 9: Brain stem in relation to cerebrum and cerebellum

Meninges and Spaces (Fig. 10): The meninges are the dura mater, the arachnoid mater, and the pia mater.

• Dura mater - a thick membrane made of dense irregular connective tissue that surrounds the brain and spinal cord.

• Periosteal membrane - the periosteal layer of the dura mater adheres to the inner surface of the skull bones while the meningeal layer lays over the arachnoid mater. Between them is the cranial epidural space. [18]
• Epidural space is a potential space between the cranial bones and the endosteal layer of the dura mater. [19]
• Meningeal layer - a durable, dense fibrous membrane that passes through the foramen magnum and is continuous with the dura mater of the spinal cord. [20]

• Subdural space (or subdural cavity) is a potential space that can be opened by the separation of the arachnoid mater from the dura mater as the result of trauma, pathologic process. [21]
• Arachnoid mater "“ The middle layer of the three meninges consisting of a network of fibers and collagen that are part of the suspension system that helps protect the brain from sudden impact. [22]
• Subarachnoid space - The interval between the arachnoid membrane and the pia mater. [23]

• Consists of the cerebrospinal fluid (CSF), major blood vessels, and cisterns. The cisterns are enlarged pockets of CSF created due to the separation of the arachnoid mater from the pia mater based on the anatomy of the brain and spinal cord surface. [24]

• Pia Mater - the meningeal envelope that firmly adheres to the surface of the brain and spinal cord. It is a very thin membrane composed of fibrous tissue covered on its outer surface by a sheet of flat cells thought to be impermeable to fluid. [25]

• The innermost layer of the meninges closely covers the brain. It acts as a barrier and aids in the production of cerebrospinal fluid. [26]

Figure 10. Protection of the CNS\

The key to understanding how an SRC occurs is that you understand the anatomy of the brain. The brain is made up of ALL the structures lying inferior to the skull. The literature reports the average distance between the skull and the brain is between 0.4 and 7 mm depending on where you measure. [27] And when we're talking about the cerebrum it is approximately 1-2 mm. [28] But in reality, this distance is incorrect! We must remember that this is the distance from the STRUCTURES (PARTS) of the brain, and NOT the distance between the SKULL AND THE BRAIN. The dura mater lies directly next to the inside of the skull. Therefore, there is NO DISTANCE (SPACE) between the skull and the brain as a whole. The meninges and spaces between them are part of the cerebrospinal fluid and ventricular system designed to protect the structures of our brain.

Figure 11. Relationship among the Brain, Cranium, and Meninges

The cranial meninges which are continuous with spinal meninges surround the brain and act as shock absorbers that prevent contact with the surrounding bones of the skull. There are three layers of cranial meninges: dura mater (outermost), arachnoid mater (middle), and pia mater innermost (Fig. 11). The dura mater is made up of two layers the periosteal/endosteal layer which attaches to the periosteum of the skull and the meningeal layer. These layers have a small gap between them which contains CSF. [10] The arachnoid mater is a membrane covering the brain and lies between the meningeal layer of the dura mater and the pia mater which is in contact with the brain. The narrow space between the arachnoid mater and the meningeal layer is called the subdural space. [10] This thin space is occupied by a serous fluid not considered CSF. [9,29] The space between the arachnoid mater and the pia mater is called the subarachnoid space. The arachnoid mater acts as a ceiling over cranial blood vessels while the pia mater is the floor. Within the subarachnoid mater the vessels are supported by the arachnoid trabeculae and surrounded by CSF. [10]

Cerebrospinal fluid (CSF) and the ventricular system of the brain are also important anatomy regarding discussion around SRC. CSF completely surrounds and bathes the central nervous system, meaning the structures of the brain and the spinal cord. CSF is also the fluid which fills the ventricles of the brain. There are four ventricles in the adult human brain. (Fig. 12) There is one ventricle within each cerebral hemisphere, a third within the diencephalon, and a fourth that lies between the pons and cerebellum and extends into the superior portion of the medulla oblongata. The two lateral ventricles do not connect with each other, but each connects with the third ventricle which connects with the fourth ventricle. [10] Two of the functions of CSF and ventricular system are preventing contact between neural structures and surrounding bones and supporting the brain structures through suspension within the skull. [30] THIS STATEMENT IS CLOSER TO THE TRUTH AS IT POINTS OUT THAT THIS SYSTEM SUPPORTS THE STRUCTURES OF THE BRAIN AND NOT THE ENTIRE BRAIN ITSELF.

Figure 12. Ventricles

The flow of CSF in the spaces along with the ventricular system is shown in Fig. 11 and Fig. 13. The pia mater is attached to the surface of the brain into fissures of the cerebrum and laminae of the cerebellum. These layers of the cranial meninges that contain the CSF and surround the brain and are part of the protective mechanism to reduce the forces causing brain injury by acting as a buffer between the brain and the skull. CSF surrounding the brain combined with flowing through the four ventricles and folds protects the brain by acting as a shock absorber and supporting the brain through suspension by providing buoyancy. [9,31]

Figure 13: CSF and Ventricular System

Regarding SRC, the anatomy of the CSF and ventricular system have two main functions, buoyancy, and protection. The actual mass of the human brain is about 1400"“1500 grams (approximately 3.09-3.31 pounds); however, the net weight of the parts of the brain inside of the dura mater suspended in CSF is equivalent to a mass of 25-50 grams (approximately .056-.11 pounds/.88-1.76 ounces). The brain therefore exists in neutral buoyancy, which allows the brain to maintain its density without being impaired by its own weight. CSF protects the brain tissue from injury when jolted or hit, by providing a fluid buffer that acts as a shock absorber from some forms of mechanical injury. [29]

THE ABOVE TWO UNDERLINED STATEMENTS ARE NOT TRUE AS THEIR STATEMENT ABOUT THE BRAIN DOES NOT INCLUDE THE MENINGES (LININGS) WHICH SURROUND THE STRUCTURES OF THE BRAIN. THE ENTIRE BRAIN IS NOT BOUYANT WITHIN THE SKULL. STRUCTURES OF THE BRAIN MAY HAVE SOME BOUYANCY, BUT NOT THE ENTIRE BRAIN. THEREFORE, THE BRAIN DOES NOT BOUNCE, FLOAT, SLOSH, SHAKE OR MOVE IN A WAVE. THIS WILL BECOME IMPORTANT TO UNDERSTAND AS WE MOVE ON REGARDING HOW MECHANICAL FORCES ACT ON THE BRAIN TO CAUSE INJURY.

Falx cerebri, Tentorium cerebelli, Falx cerebelli, and Diaphragma sellae

At four locations of the dura mater there are folds of the meningeal layer which extend deep into the cranial cavity. These extensions subdivide the cranial cavity and provide support for the brain by limiting brain movement.

The falx cerebri (Fig. 14) is a fold of dura mater which projects down between the cerebral hemispheres to the longitudinal fissure right above the corpus callosum. The tentorium cerebelli (Fig. 14) supports the two occipital lobes of the cerebrum and separates the cerebellar hemispheres from those of the cerebrum. It extends across the cranium at right angles to the falx cerebri. The transverse sinus lies within the tentorium cerebelli. The falx cerebelli extends in the midsagittal line inferior to the tentorium cerebelli, dividing the two cerebelli hemispheres. It contains the occipital sinus.[10]

These folds are made up of the meningeal layer of the dura mater and are described as a dense fibrous membrane meaning they are stiffer than the surrounding brain tissue. The mechanical function of these dural folds is to limit the rotational displacement of the brain and support the brain by dampening motion in the brain. [32,33]

Figure 14. Falx cerebri and tentorium cerebellum

Corpus callosum (Fig. 15) is a thick bundle of nerve fibers that connects the left cerebral hemisphere with the right hemisphere allowing information to be passed between them. It ensures that both sides of the brain can communicate and send signals to each other. But one of the other functions of the corpus callosum which is not recognized is the structural support for the cerebral hemispheres. The corpus callosum is approximately 10 cm in length, 2.5 cm in height. [34,35] It is the largest white matter structure in the human brain consisting of approximately 200"“300 million axonal projections. A number of separate nerve tracts, classed as subregions of the corpus callosum, connect different parts of the cerebral hemispheres. [34,36]

This collection of white matter within the brain has a high myelin content. [37] Myelin increases the stiffness of white matter which is what makes the corpus callosum a supportive structure for the cerebral hemispheres. [38,39] This is extremely important in the structural and mechanical function of the corpus callosum and how it provides some protection of the brain against injury.

Figure 15. Corpus callosum

Cerebral Peduncles and Cerebellar Peduncles (Fig. 16)

The cerebral peduncles attach the cerebral hemispheres to the brainstem just below the thalamus and above the pons. The cerebellar peduncles attach the cerebellar hemispheres to the brain stem laterally and posteriorly at the pons. The key to mentioning these two structures of the brain is that together they connect approximately 90-95% of the brain's weight to the brainstem.

Figure 16. Cerebral and cerebellar peduncles

Review of the Structural Anatomy of the Brain Important in Understanding the Mechanism of Injury to the Brain.

1. All structures inferior to the skull constructs the brain.
2. The brain is separate from your skull. The brain does not attach to the skull.
3. The brain has no attachment to your skeletal body. Human anatomy possesses no muscles which can provide movement to the brain within the skull. The brain only moves in reaction to head and body movement.
4. Fluid inside our skull is contained within the brain. No fluid or space is between the brain and the skull.
5. The brain has its own structural and mechanical system to protect itself from injury in addition to the support structure provided by the head, neck, torso, upper and lower extremities.

Based on human anatomy and anatomical structure of the head, neck, and brain there has never been direct contact with the brain through either a direct impact to the head/helmet or an indirect impact to the body causing a SRC. Therefore, we can conclude that there are other mechanical forces acting upon the brain after any impact that causes a SRC. And if that is the case, why has HeadHealth Technology relegated itself to the position that absorption on direct contact to the head via a helmet is the only way to prevent SRCs.

HELMET DESIGN

When the football helmet evolved and became a hard outer shell with its shape what was it designed to do? A helmet causes a skid upon impact because its smooth, hard outer shell allows the head to slide across the surface it hits instead of abruptly stopping, which helps to dissipate the force of the impact and minimize the strain on the neck by distributing the energy over a larger area during the slide; essentially, the helmet "skids" rather than abruptly stopping upon contact, reducing the potential for serious head injuries. [74] In 1939, the Riddell Company of Chicago, Illinois started manufacturing plastic helmets because it felt that plastic helmets would be safer than those made of leather. Plastic was found to be more effective because it held its shape when full collision contact occurred on a play. [75] We know that Force = Mass x Acceleration. From this we also know if two helmets impacting each other abruptly stop upon contact it means they remained in contact for a longer period of time and more force is transferred. Therefore, we make the assumption that the less time on contact the less force is transferred. Part of this design of a hard outer shell was to deflect the blow creating less time of contact in order for less time of transfer of force.

Today the purpose of the design of a helmet has changed. Helmets are designed mainly to dissipate force. Most sports helmets consist of a hard outer shell and an inner foam layer, normally of polystyrene. The hard shell spreads or dissipates the impact force over a larger area. Meanwhile the foam inner section also reduces the peak impact by extending the distance of head deceleration "“ meaning that it takes longer for the head to slow down, which makes the movement less abrupt. The foam layer also crushes and deforms, which absorbs as much of the remaining energy as possible. [76]

HELMET TESTING RESEARCH

Over the last 10-15 years millions of dollars have been spent on "head health technology". The term HeadHealth was introduced by the National Football League through initiatives called the NFL HeadHealthTECH Challenge and the HeadHealth Challenge. [40,41] The HeadHealthTECH Challenge is a series of innovation challenges intended to deepen understanding of and advance solutions in the areas of head protection, material science and kinematic measurement, among others. The TECH Challenges are structured to stimulate research and innovation, as well as encourage connections with mentors and/or venture capitalists, with a goal of spurring developments in engineering, biomechanics, advanced sensors, and material science. [40] As a result, research and testing around the helmet has increased over the last 10 years. A critical component of concussive injuries is how the mechanical energy from the external input to the head/helmet (acceleration/deceleration of the head/helmet) is transferred to the brain and vascular tissue at the tissue and microscale. This energy transfer process"”both how the acceleration/deceleration moves and deforms the brain tissues and the effect of this physical stimulus on the living tissue and neural/glial networks"”is the key step in understanding the basis for concussion. [42] As a result of my review of the research and testing of helmets the majority has been focused on peak linear acceleration (PLA), peak rotational acceleration (PRA), impact duration (IMPD), and recently impact location (IMPL) has been incorporated into the mix. [43,44,45,46,47] Although to date, I do not believe there has been any consensus on exactly what factors or criterion established from these measures bring us any closer to determining what results in SRC. Even though we believe injury mechanisms are likely related to kinetic measures of impact severity (e.g. peak linear acceleration (PLA), peak rotational acceleration (PRA), and impact duration (IMPD), it remains unclear if any single biomechanical measure is well correlated with the occurrence of MTBI. [44]

And I base this on the NFL and NFLPA Helmet Testing Performance Results. From 2018-2024 the NFL and NFL Player's Association have together released their extensive laboratory and on-field performance testing results. [48,49,1,2,3,4,5] In 2018, there were 17 helmets in the top performing group which consisted of helmets whose performance were not statistically different from the two top ranked helmets in the group. [48] The 2019 tests reported 27 helmets in the top performing group of helmets in which there was no statistical difference from the top three helmets in the group. [49] In 2020 their rhetoric changed regarding performance results. They identified 31 helmets with "˜better laboratory performance' but distinguished the helmets into two groups. The testing identified 15 out of 31 helmets that performed better in laboratory testing than the other 16 approved helmets. [1] The 2021 laboratory results included 20 helmets in the top performing group with 12 helmets that performed better in laboratory testing. [2] In 2022 there were 21 helmets in the "˜better laboratory performance' group with 15 helmets identified as performing at a higher standard in the laboratory. [3] 2023 had 19 helmets in the "˜better laboratory performance' group with helmets identified as performing higher. [4] And now in 2024 NFL and NFLPA Helmet Laboratory Testing Performance Results have separated their results into four specific categories: overall, offensive lineman, defensive lineman, and quarterbacks. [5] The number of helmets in each category is different: 18 ranked helmets in the overall testing results, 19 ranked helmets in the offensive and defensive lineman results, and 16 helmets in the quarterback category. A summary of the number one results/rankings are as follows: Overall category-Riddell Axiom 3D (R61227-New); Offensive Line-Xenith Orbit Pro (New); Defensive Line- Xenith Orbit Pro (New); and Quarterback-VICIS ZERO MATRIX ID QB (19016). Other observations of the testing show that the Riddell Axiom 3D (R61227-New) finished third in all position categories; the Xenith Orbit Pro (New) finished second in the overall and quarterback categories; and the VICIS ZERO TRENCH MATRIX ID 2024 (19017) (New) finished second in the offensive and defensive line categories.

QUESTIONS: How is the Riddell Axiom 3D helmet which finishes number one overall not in the top position of any of the position categories? How is the VICIS TRENCH helmet ranked number two in the offensive and defensive line categories and not even ranked in the overall category? And last, but not least, why are no specific kinematics of test results ever shown with the performance testing results?

What is the NFL and NFLPA Helmet Testing Performance Results based upon? The NFL uses kinetics to test football helmets by evaluating how well they manage the forces and motions associated with concussions. The NFL's helmet testing protocol considers both linear acceleration and rotational kinematics of the head. [50]

POTENTIAL ENERGY AND KINETIC ENERGY

Helmets are designed to absorb energy upon contact in order to reduce forces which act upon the head and in turn the assumption is that force will be reduce to the brain. The helmet can only absorb energy and protect the head upon direct contact with another object. As the general public we have been led to believe via NFL helmet testing and research that the helmet is the only method of protecting against SRC. But, in order to fully understand what is happening to the brain during a SRC event and how helmets are designed to protect the head we also need a quick review of the science and physics behind the energy believed to cause SRC.

The energy acquired by the objects upon which work is done is known as mechanical energy. Mechanical energy is the energy that is possessed by an object due to its motion or due to its position. Mechanical energy can be either kinetic energy (energy of motion) or potential energy (stored energy of position). In physical sciences, mechanical energy is the sum of potential energy and kinetic energy. [51] In physics, potential energy (PE) is the energy held by an object because of its position relative to other objects, stresses within itself, its electric charge, or other factors.[52] In physics, the kinetic energy (KE) of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate the body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes. [53] In Newtonian mechanics, linear momentum, translational momentum, or simply momentum is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and direction. [54] Inertia is the resistance of any physical object to any change in its velocity. This includes changes to the object's speed, or direction of motion. An aspect of this property is the tendency of objects to keep moving in a straight line at a constant speed when no forces act upon them. [55]

COUP "“ CONTRECOUP BRAIN INJURY

Before we begin our discussion of SRC we also need to define coup vs. contrecoup injury of the brain. The terms coup and contrecoup are French for "blow" and "counterblow." Therefore, a coup-contrecoup injury actually refers to two separate injuries. [56] A coup injury occurs on the brain directly under the point of impact. A contrecoup injury occurs on the opposite side of the brain from where the impact occurred. [56,57] For the purpose of the following description of what occurs to the brain in a SRC, the side of the brain which is the first contact with the skull will be the coup side and the opposite side of the brain contacting the skull will be the contrecoup side.

WHAT HAPPENS INSIDE THE SKULL?

The pathology of concussion has been attributed to rupture, shearing, contusion, stretching and tearing of the various structures (parts) within the brain. Those structures include veins, nerves, cerebrum, cerebellum, midbrain/brain stem, and spinal cord. As I pointed out previously the brain is not attached to the skull and therefore when impact is applied to the head/helmet that is not impact to the brain. The brain only moves in reaction to how the head moves. When an impact occurs to the head/helmet the force which occurs is only elicited to the head/helmet. The force which occurs within the brain is the force created by its own kinetic energy of motion caused by its reaction to the head/helmet motion, thus making it independent of the impact to the head/helmet. This is where we have to change our thinking and our hypothesis of how the brain is injured from direct and indirect impacts.

SRC occurs from direct impact, a bump, blow, or jolt to the head, or from indirect impact, that causes the head to move rapidly back and forth. The key in these mechanisms of direct and indirect contact is there is an acceleration and/or deceleration motion of the head that occurs causing a SRC! Motion and some type of impact are always involved. The Impact duration (IMPD) of the head/helmet is the time period when two or more bodies collide. Head/helmet impacts have been recorded as having an IMPD between 5.5 and 13.7 milliseconds (ms). [45] When a head/helmet in motion comes in contact due to direct impact, the head/helmet is stopped during IMPD and changes direction. This is when a head/helmet goes from acceleration to deceleration and to acceleration again. At some point in time the head/helmet comes to zero velocity at the impact location (IMPL) before moving in the opposite direction. Contact with the head/helmet causes mechanical energy to be transferred to the head/helmet by its position. We must understand that the absorption of energy from the head/helmet only occurs at this point and during this timeframe of contact. The only place and time a helmet can provide protection to the brain through absorption of energy is at the IMPL for the duration of the impact (IMPD) and only during a direct impact. This absorption of energy via the head/helmet is absorption which prevents force elicited to the skull not to the brain. Force elicited upon the brain ONLY occurs after the IMPD. Because the brain is separate from the skull and does not accelerate and decelerate at the same time the head accelerates and decelerates. The force to the brain occurs as result of its movement within the skull in response to the head/helmet movement created from direct and indirect impacts. Our brain was designed with its own ability to absorb the forces elicited to it through its own mechanical and structural anatomy. SRC occurs when those forces cannot be protected by the skull and the kinetic energy created by motion cannot be absorbed by the mechanical and structural anatomy of the brain.

Based on the NFL-NFLPA Helmet Testing Performance Results, NFL promotion of safety via helmets, and the information fed to us by the football helmet companies, we have been led to believe that the most energy elicited to the brain is caused by direct contact to the head/helmet. Yet we know concussions occur through indirect contact also. Based on the mechanical and structural anatomy of the brain designed to absorb its own forces we must ask ourselves two questions: 1) Is direct contact the only place where there is energy being elicited to the brain causing stress and strain to its anatomical structures which produces SRC?; and 2) Is direct contact to head/helmet where the brain's kinetic energy of motion upon deceleration of head elicits the most force on the brain?

HEAD/HELMET IMPACTS IN FOOTBALL

Direct Impact "“ a mechanism of injury (MOI) in which direct contact to the head/helmet causes SRC.

1. Helmet-to-helmet contact in which both helmets are moving with a measurable velocity.

1. A linebacker's helmet hits a running back's helmet while making a tackle.

1. Helmet-to-helmet contact in which one helmet's velocity is much greater than the helmet with which it is impacting.

1. Kickoff return blocker setting up to block opponent who is running down in kickoff coverage gets direct hit to helmet which causes violent head/helmet motion after contact.

1. Helmet makes contact with an immovable object.

1. Quarterback drops back and gets hit in the chest being tackled and his head/helmet whips into the ground/turf.

Indirect Impact "“ a MOI in which there is no contact with the head/helmet that causes SRC.

4a) Body-to-body contact in which both players are moving with a measurable velocity.

1. Wide receiver crosses the middle of field and defensive back makes shoulder to body contact causing head/helmet to move violently.

4b) Body-to-body contact in which one player is moving with a measurable velocity and the other player is stationary.

1. Safety blitzes from his position hitting the quarterback setting up to pass causing the head/helmet to whip.

WHAT HAPPENS TO THE BRAIN WITH IMPACTS?

#1: Helmet-to-helmet contact in which both helmets are moving with a measurable velocity.

Player 2, a linebacker, and player 1, a running back are both moving toward each other and make helmet to helmet-to-helmet contact as Player 2 attempts to tackle Player 1. The impact duration (IMPD) of the head/helmet is the time period when two or more bodies collide. Head/helmet impacts have been recorded as having an IMPD between 5.5 and 13.7 milliseconds. [45] The impact from player 2's helmet in some way contacts player 1 causing player 1 to sustain a concussion. Player 1's head/helmet and brain are moving at the same speed when contact is made (Fig. 15: Player 1-left, Player 2-right). Upon contact player 1's head/helmet forward motion is stopped and comes to zero velocity during impact and changes direction after contact. The question we must ask ourselves is, "Does the brain come to zero velocity at the same time as the head/helmet?"

Figure 15

LABEL PLAYER 1 AS THE HEAD ON LEFT AND PLAYER TWO AS HEAD ON RIGHT

Since the brain is not attached to the skull we must assume when the head/helmet stops at impact, the brain which has its own momentum and inertia will continue moving separately from the head/helmet inside the skull in the same direction as the head/helmet was moving prior to being stopped by the impact. When the head/helmet abruptly decelerates on impact coming to zero velocity, the brain, since it is separate, continues to move into the inferior surface of the skull (Fig. 16). The coup side of the brain was next to the inferior aspect of the skull at IMPL; therefore, it remains in contact at this location. While the contrecoup side of the brain opposite of the impact continues moving toward the IMPL and compresses. The inferior surface of the skull did not cause force to be elicited to the brain, but the kinetic energy of motion that the brain has during its continued motion toward the skull where the IMPL occurred outside the skull is what causes forces to act on the brain.

Figure 16

Therefore, it is the abrupt deceleration of the head/helmet causing the brain to compress into the inferior surface of the skull. The impact is to the head/helmet and not the brain. As mentioned previously, many theories have described the brain as bouncing, floating, sloshing, shaking, moving in waves, and now we even have experts describing the motion of the brain from impacts as "lagging behind and trying to catch up to the skull". [6] The following video is the most recent demonstration I have found that tries to depict brain movement upon contact: https://www.youtube.com/watch?v=yPCr5yQDOLs [58] This model reflects the statement made by David Camirillo, whom many consider and expert in brain research, "So, one thing that I do agree with, and I think most experts would, is that the brain does have these dynamics. It does lag behind the skull and then catches up and moves back and forth and oscillates. Your brain is one of the softest substances in your body, and you can think of it as kind of like Jello." [6] As you can see, this video depicts the brain as bouncing and then moving in a wave and oscillating following direct impact.

Based on the structural anatomy of the brain, what is the problem with this theory of how the brain reacts to direct contact in the video? Number one, the brain in this video does not have any membranes surrounding the brain model and therefore does not account for the dura mater which lies next to the skull. Number two, the brain model is not in contact with the inferior surface of the skull. And number three, there are no fluid or ventricles within this model which are how the brain has been designed to absorb its own forces created by its own kinetic energy of motion in reaction to the head's movement .

And based on the demonstration depicting a direct blow in this video, what is the issue? Movement of the head/helmet does not stop to zero velocity with no motion following a direct impact. Helmets are designed to deflect the blow. Why? Less time on contact, less force transferred. Therefore, the head/helmet changes direction after it comes to zero velocity with a new velocity. Which brings us back to the question, "Does the brain come to zero velocity at the same time as the head/helmet?"

The average weight of the head is 11 pounds, and the average weight of the brain is about 3 - 3.3 pounds. [59] Therefore, the assumption is the skull weighs 8 pounds. The average weight of a football helmet is approximately 3-5 pounds. The head/helmet then weighs approximately 11-13 pounds, and the head/helmet and brain together weigh approximately 14-16 pounds.

Since there are forces that act upon the brain after impact, we need to examine what happens after impact. In order to do this, we need to understand the head/helmet and brain as it relates to mechanical energy. As previously stated, player 1's head/helmet and brain are moving at the same speed when contact is made with player 2. Therefore, there is a momentum of 14-16 pounds when player 1's helmet is directly impacted by player 2. Helmets are designed to absorb energy from an impact, thereby reducing the force transmitted to the head. [60] But it is key to remember that the brain is not attached to the skull and is a separate entity from the head/helmet. Though the coup side of the brain is directly next to the skull and therefore has minimal movement at the direct IMPL as the rest of the brain continues its kinetic energy of motion with the contrecoup side separating from the inferior surface of the skull and compressing toward the IMPL. (Fig. 16) This continues to occur even after the head/helmet abruptly decelerates on impact to zero velocity because the brain, since it is separate, still has its own 3-3.3 pounds of momentum and inertia. The brain does not come to zero velocity at the same time as the head/helmet during impact. The energy being absorbed by the head/helmet has no effect on the reduction of force to the brain during impact. Just prior to this change of direction of the head/helmet at zero velocity, whatever kinetic energy has not been absorbed by the head/helmet becomes PE of the head/helmet.

The question now becomes what happens to the brain AFTER THE IMPD of the head/helmet where both helmets are moving when they make contact? Player 1's head/helmet came to zero velocity and then changed directions. We know that the coup side of the brain was in contact with the inside of the skull, but is the contrecoup side through its own KE of motion still moving toward the IMPL as the head/helmet changes direction? Yes, based on the laws of science this is shown in (Fig. 16) At zero velocity the head/helmet now has potential energy (PE) again. As the head/helmet with its own KE begins moving away from the IMPL the brain creates its own IMPD with the skull and is still coming to its own zero velocity. Now as the head/helmet continues to move in the opposite direction from the IMPL the inside surface of the skull is pushing on the coup side of the brain while the contrecoup side of the brain is still compressing. (Fig. 17) The brain's PE at zero velocity is now being changed to kinetic energy of motion in the opposite direction by the head/helmet.

Figure 17

This is where we begin to fail in how we are trying to prevent concussion in football. We now have KE of motion created by the momentum of the head/helmet and transmitting KE of motion to the brain, and each accelerating with its own inertia and momentum which is the reason for the belief that the brain lags behind. The truth is that this has to occur, or we would never have a whiplash concussion. Inertia is the resistance of any physical object to any change in its velocity. This also means that the brain is not bouncing around on its own inside the skull! The inferior surface of the skull PUSHES the brain as a result of the motion created to the head/helmet after impact. As the head/helmet is now moving away from the IMPL it has a momentum of 12-13 pounds and a brain which has 3-3.3 pounds of momentum. Obviously, the brain accelerates with less velocity than the helmet/head which is why it is being pushed on the coup side and the assumption that it lags behind. This then implores the question, "Does the coup side of the brain stay in contact with the skull until the head/helmet reaches zero velocity in its movement away from the IMPL, or does it separate prior to helmet/head movement? We have already concluded the brain does not reach zero velocity at the same time as the head/helmet, therefore when the head/helmet moves away from the IMPL the coup side of the brain stays in contact with the skull being pushed by the head/helmet moving in the opposite direction from IMPL. The contrecoup area of the brain increased its distance away from the back of the skull during IMPD. But as the head/helmet has changed direction and is now pushing the brain away from the IMPL the contrecoup side of the brain is expanding back to its normal shape. The head/helmet and brain now each have their own kinetic energy still needing to be absorbed accelerating in a direction away from the IMPL. The brain with its own momentum continues to accelerate with the contrecoup side of the brain leading the way as the coup side is being pushed by the skull. What happens now with the brain when the head/helmet whips to a stop, comes to zero velocity, and changes direction after its acceleration away from IMPL? The contrecoup side of the brain is still separate from the inferior skull and the coup side is no longer in contact as it is not being pushed any more. At the moment the head/helmet reaches zero velocity, neither the coup nor contrecoup sides of the brain are now in contact with the inferior surface of the skull and the brain continues its motion toward the inferior surface of the contrecoup side of the skull. Fig. 19

Figure 19

Now as the head/helmet reverses its direction moving back toward the initial IMPL and the contrecoup side of the skull makes contact with the brain while the brain is still moving toward it. (Fig. 20)

Figure 20

In this situation the inferior surface of the skull is initiating contact with the contrecoup side of the brain. This is the location of the FIRST DIRECT IMPACT TO THE BRAIN! Is there more force being elicited to the brain at this IMPL or upon the brain at the initial head/helmet IMPL? Now the head/helmet begins PUSHING the contrecoup side of the brain back toward the impact site as the coup side is still compressing. (Fig. 21.)

Figure 21

This continues until the entire momentum of the brain changes to moving in the same direction as the head/helmet. (Fig. 22)

Figure 22

#2: Helmet-to-helmet contact in which one helmet's velocity is much greater than the helmet with which it is impacting. Player 2 has run back for a kickoff return and is setting up to block Player 1, the opponent who is sprinting down on kickoff coverage. Player 2 steps in to block Player 1 and helmet to helmet contact occurs with the impact causing Player 2 to sustain an SRC. In this helmet-to-helmet impact Player 2's head/helmet has no motion or minimal motion toward Player 1's helmet which is moving with a very significant amount of velocity when contact is made. Therefore, Player 2's head/helmet and brain are basically at zero velocity or an insignificant velocity when impact occurs. Fig. 23

Figure 23

TAKE ALL 4 RED ARROWS OUT OF PLAYER 2'S BRAIN. LABEL PLAYER 1 (LEFT) AND PLAYER 2 (RIGHT) BELOW THEIR HEAD IMAGES.

Upon contact the helmet absorbs as much energy as possible prior to the kinetic energy of head/helmet movement away from its position of zero-velocity at IMPL. Since the brain was also at zero-velocity upon contact, brain movement away from the IMPL is initiated by the inferior surface of the skull at IMPL pushing the brain posteriorly. In this contact to contact hit it is the head/helmet which begins PUSHING on the brain at IMPL. The coup side of the brain is now being pushed into motion by the skull transferring kinetic energy throughout the brain via the momentum of the head/helmet caused by the push. Now both the head/helmet and brain are moving, each creating its own velocity through the kinetic energy of motion. The question now becomes what happens to the brain? Based on the laws of science the head/helmet's motion away from the IMPL causes the inferior surface of the skull to begin pushing the coup side of the brain toward the contrecoup side. Since the brain's momentum is less than the head/helmet the contrecoup side of the brain separates from the skull creating space between itself and the skull. This causes compression of the brain from the coup to the contrecoup side. (Fig. 24)

Figure 24

The coup side would continue moving and compressing the contrecoup side of the brain until the entire momentum of the brain was moving away from the IMPL resulting from the acceleration of the head/helmet. (Fig. 25)

Figure 25

REMOVE IMPACT ARROW AND IMPACT LOCATION (ON LEFT) FROM THE ABOVE FIGURE 25

This head/helmet and brain will continue with this motion until the head/helmet whips to zero velocity away from the initial IMPL. (Fig. 26)

Figure 26

REVERSE THIS ENTIRE PICTURE "“ FIGURE 26

The head/helmet whips back toward the IMPL and strikes the brain. And this compression would increase as the head/helmet moves out of zero velocity from its momentum and changes direction moving back toward the IMPL by pushing the contrecoup side of the brain back toward the coup side as it continues its motion in the opposite direction. (Fig. 27)

Figure 27

This movement back toward IMPL continues until both the head/helmet and brain are moving in the same direction.

Figure 28

Where again the head/helmet whips to zero velocity in this direction back towards IMPL. The brain compresses again until the head/helmet changes direction and begins pushing the brain in the opposite direction. This continues until the head completely decelerates and comes to a stop

In both of the scenarios #1 and #2 above, direct contact in which both player's head/helmet is in motion with velocity, and direct contact in which one head/helmet has velocity and the other has minimal motion, absorption of energy by the helmet can only protect the first mechanism of brain movement causing concussion. After the initial direct helmet-to-helmet contact where the contrecoup side of the brain compresses toward the coup side at IMPL, the helmet will do nothing in reducing the force and energy which is elicited to the brain from head/helmet movement after impact!

This leads to the SAME QUESTION we asked in scenario #1, is more force elicited to the brain on the coup side at IMPL during IMPD, OR on the contrecoup side when the skull elicits force to the brain on its return toward IMPL after whipping to a stop and changing direction? We must remember that the brain's own KE of motion is what elicits forces within the brain.

#3: Helmet makes contact with an immovable object. What happens to the brain when a player goes to the ground with direct contact of the helmet to the turf? Player 1 drops back to pass and is rushed by Player 2 who hits Player 1 in the chest forcing Player 1 to fall to the turf backwards to the turf causing the posterior aspect of their head/helmet to whip into the turf. Initially Player 1's head/helmet will begin to push the brain anteriorly from the hit into the chest as the head begins to whip in a forward direction. (Fig. 29)

Figure 29

The head/helmet will continue tO accelerate anteriorly in this direction until it whips to a stop and begins pushing the brain in the opposite direction posteriorly. (Fig. 30) The head/helmet and brain are now moving posteriorly with the body as all are falling and being forced to the turf from the tackle. (Fig. 31)

Figure 30 Figure 31

The force of the hit from player 2 will determine the speed that the body and head/helmet of Player 1 are moving when they hit the turf. We can assume that since the head/helmet is whipped posteriorly from a position more anteriorly than the body after the initial hit, its acceleration will be much greater than that of the body. As the body hits the turf the head/helmet continues forcefully into the turf coming to zero velocity much more rapidly than any other impact that occurs in football. (Fig. 32)

Figure 32

REVERSE THE HEAD AND BRAIN IN THIS PICTURE "“ FIGURE 32

The head/helmet rebounds off the turf, changing the brain's momentum to the opposite direction until the whole brain is moving in the same direction as the head/helmet. (Figure 34 and Figure 35)

Figure 34 Figure 35

#4A: Body-to-body contact (indirect impact) in which both players are moving with a measurable velocity. Player 1, wide receiver catches a pass over the middle and is hit by Player 2, defensive back in the shouder allowing Player 1's head to continue forward and then whip backward. Whiplash is defined as an abrupt snapping motion or change of direction resembling the lash of a whip. [61] . In its cause of a SRC, whiplash is the forceful, rapid back and forth movement of the head and neck from an indirect impact to the body. In this impact, even though the body has come to zero velocity, the head/helmet continues its motion forward. The coup (posterior) side of the brain is being pushed by the inferior surface of the skull. (Fig. 36)

Figure 36

This movement of the head/helmet and brain continues forward with increased velocity through momentum until the head/helmet comes to zero velocity. (Fig.37)

Figure 37

REPLACE POINT OF IMPACT WITH ZERO VELOCITY LINE IN FIGURE 37

After the whip to zero velocity the head/helmet through changes direction, striking the contrecoup (anterior) side of the brain, and begins to push the brain in the opposite direction. (Fig.38)

Figure 38

REMOVE THE NOSE ON THE RIGHT IN FIGURE 38

The head/helmet continues pushing the brain posteriorly until it reaches zero velocity. (Fig. 39) The head/helmet changes direction again coming back anteriorly, striking the brain, bringing it to zero velocity and changing its direction again. (Fig. 40)

Figure 39 Figure 40

#4B: Body-to-body contact (indirect impact) in which one player is more stationary, and the other is moving with a measurable speed. Player 1, the quarterback sets up to pass in the pocket and Player 2, a safety coming on a blitz from the right hits the quarterback in the back upper torso causing the head to whip posteriorly and then anteriorly. This initial motion will cause the head/helmet to begin pushing the brain posteriorly. (Fig. 41)

Figure 41

The head/helmet will continue to accelerate posteriorly pushing the brain in the same direction. (Fig. 42)

Figure 42

This continues until the head/helmet whips to zero velocity and reverses its direction and strikes the brain which is still moving posteriorly and reverses its direction . (Fig. 43 & 44)

Figure 43 Figure 44

This head/helmet continues to push the brain until both are moving completely in the same direction until the head/helmet reaches zero velocity in the opposite direction. (Fig. 45)

Figure 45

HOW IS ENERGY ABSORBED BY THE HEAD, NECK, AND BRAIN TO PREVENT CONCUSSION?

The Head

The two main functions of the skull are its bony structure which forms a cavity for the brain to protect it from injury and support the face. [62] The skull also provides attachment sites for neck musculature which have been proposed to prevent brain injury through deceleration of the head/helmet.

The Neck

Neck strength is increasingly gaining recognition as a potentially modifiable risk factor for sport-related concussion however the evidence remains equivocal. The verdict of whether strengthening the musculature of the neck can help in reducing the occurrence and incidence of concussion is still debatable. It would seem sensible that since the muscles of the neck are responsible for moving the head that they would have some function in helping slow down the head and therefore the brain after impact, but the evidence is contradictory.

Basically, the literature reports that increased neck stiffness (resistance of motion) is suggested to improve an athletes' ability to absorb external forces by allowing for more even distribution of kinetic energy through the torso. [63] Purportedly if you can pre-activate the muscles of the neck which support the head this will increase neck stiffness and will help reduce translational velocity, meaning if you know the impact is coming you have a better chance of muscle firing and recruitment which might help in preventing excess head motion and protect the brain. [64,65]

This is where the dilemma of helmets comes into play. We know heavier helmets absorb forces better, but due to momentum and inertia put the neck at risk for greater injury, especially for youth players. The entire movement of the head and neck after IMPD is to absorb the energy from the head/helmet that is in excess of the head/helmet's ability to absorb energy during IMPD. Heavier helmets definitely add to the speed of brain movement and change of direction caused by movement of the helmet/head after initial impact which increases force and energy acting upon the brain and the neck. A lighter helmet is no doubt safer for the brain and the neck after initial impact in direct hits and on indirect hits.

The Brain

This movement after IMPD of the head now transfers from the skull to the brain causing it to move inside separate from the skull. During this time, the neck muscles are trying to absorb energy and slow down the head/helmet if and only if they have been able to fire! The brain is trying to absorb energy and slow itself down separate from the skull through how God designed it. This is mainly done through cerebrospinal fluid (CSF) in the sinuses and the four ventricles within the brain forming the ventricular system of our brain (Fig.12).

We already mentioned two of the functions of CSF are to prevent contact between neural structures and surrounding bones and support the structures of the brain through suspension within the skull. [30] Therefore, working with the ventricles this system cushions and acts as a buffer for the cortex. [31] We know based on the composition of the four areas of the brain (cerebrum, cerebellum, brainstem, and meninges) they continue to move inside the skull after impact and will continue to move until the head stops moving. As a result, the CSF continues to flow and move until the brain stops moving.

We know the head will continue to move after impact until the muscles of the neck can stop it from moving. And we know that the brain continues to move inside the skull for a period after the head stops moving. I've already mentioned based on Camirillo's statement that the hypothesis the experts believe to be true is that the brain continues to oscillate after impact much like Jello. [66] I believe the CSF flows through the ventricles in more of a wave type movement and around the brain to continue to absorb the energy elicited at impact and is what brings the brain to a stop after impact. Which is why I don't necessarily think it oscillates (jiggles back and forth). CSF continues to flow to provide protection to the brain throughout movement of the head and after the head stops moving.

Heavy Helmets

The heavier helmet increases the velocity of the head and the brain after impact through the momentum it creates. As a result, increased mechanical energy is transferred to the brain as kinetic energy of motion which must be absorbed after impact or during whiplash form an indirect impact. Which is why it is extremely important that we slow down the head/helmet and bring it to a stop as soon as possible after impact. The sooner the head/helmet stops moving the sooner the brain can complete its own absorption of excess energy after impact.

In addition to the anatomy of the ventricular system of the brain designed to absorb energy and protect our brain we must attempt to understand movement of the brain based on its anatomy. We must do this as there is no way at this time to be able to capture a live view of the brain moving during impact and afterwards. Although there has been some modeling developed, I do not know of any modeling at this time which includes a replication of CSF and ventricles or an accurate modeling of how the brain works to absorb its own forces created by its own kinetic energy or how the neck functions to slow down the head after direct and indirect impacts. To do this we must take a closer look at the anatomy of the brain to hypothesize about how it moves and begin biomechanically testing these hypotheses.

ANATOMY WHICH REQUIRES A CLOSER LOOK IN EVALUATING CONCUSSION

The corpus callosum (Fig. 16 &17) is a thick bundle of nerve fibers that connects the left cerebral hemisphere with the right hemisphere. It ensures that both sides of the brain can communicate with each other. The corpus callosum is approximately 10 cm in length and 2.5 cm in height. When there is impact to the head the two hemispheres of the cerebrum are obviously moving in varying directions about the corpus callosum and the brain stem. Especially with rotation.

Figure 46: Coronal view of corpus callosum Figure 47: Sagittal view of corpus callosum

The following link depicts one theory about movement of the brain following impact which effects the corpus callosum and possible long-term damage to the brain.[66] https://www.nytimes.com/interactive/2017/01/09/sports/football/what-happened-within-this-players-skull-football-concussions.html

This theory of movement of the brain was developed by the bioengineer David Camarillo and his team in the Cam Lab at Stanford University. Camarillo and others have speculated that the most damaging blows are those that cause the head to snap quickly from ear to ear, like the one shown in the link above, or those that cause a violent rotation or twisting of the head through a glancing blow. "The brain's wiring, essentially, is all running from left to right, not front to back," Camarillo said, referring to the primary wiring that connects the brain's hemispheres. So, the direction you are struck can have a very different effect within the brain. In football, the presence of the face mask can make that sort of twisting even more extreme." [66]

The corpus callosum shows long-term damage from repeated SRC and subconcussive blows. (Fig. 48) Yet no one has theorized why or determined how the corpus callosum is being damaged.

Figure 48

there is more to the brain anatomy and possibly why a lesser force causing rotation of the head leads to more concussions than a force from the front or side. This is related to where the cerebrum and the cerebellum attach to the brain stem. Let's begin with the cerebrum. As talked about previously the total weight of the brain is approximately 1400 to 1500 grams or 3.0 to 3.3 pounds. [12, 15] If the cerebrum makes up 80-85% of the brain's weight the cerebrum weighs approximately 1200 grams or 2.6 pounds. [15] The brainstem consists of thalamus, hypothalamus, midbrain, pons, and medulla oblongata which connects with the spinal cord. The cerebral peduncles (Fig. 49) attach the two hemispheres of the cerebrum inferiorly to the brain stem in the midbrain just below the thalamus and above the pons.

The cerebellar peduncles (Fig. 49 & 50) attach the two hemispheres of the cerebellum to the brainstem at the level of the pons just above the medulla oblongata.

Figure 49: Location of cerebral and cerebellar peduncles Figure 50: Cerebellar cortex and peduncles

For our purposes of explanation, we are going to use the high end and approximate the total weight of the human brain as 1500 grams or 3.3 pounds. The total weight of the cerebrum and cerebellum together is approximately 1340 grams or 2.95 pounds. This is approximately 90% of the total weight of the brain. In vertebral anatomy the brain stem is considered part of the brain. Which means the brainstem consisting of the midbrain (mesencephalon), pons (metencephalon), and medulla oblongata (myelencephalon), the thalamus, hypothalamus, meninges, and CSF approximately make up the remaining 10% of the weight of the brain. [10] The weight distribution of the parts of the brain along with where the cerebrum and cerebellum attach to the brainstem becomes extremely important when evaluating the magnitude of force and direction of force elicited to the head at impact which causes a concussion.

The movement of the brain like other structures can move in six degrees of freedom (Fig. 51). The degrees of freedom are the ways our bodies and other objects are able to move through the space around us. The brain can move front to back on the y-axis, side-to-side on the x-axis and up and down on the z-axis. The brain can also rotate around each axis. Helmet testing measures these 6-degrees of freedom. [67]

Figure 51: Axes and planes of the brain

For evaluation of impact forces to the head which cause SRC we need to understand how the brain moves inside the skull. A force to the front of the head/helmet or to the body which causes the head/helmet to move forward and backwards with flexion and extension at the neck produces brain movement in the sagittal plane and rotation around the x-axis. Depending on the amount of movement this can cause a coup-contrecoup injury to the anterior and posterior cerebrum and to the cerebellum (Fig 52). The movement of the head/helmet in a direct impact to the front is extension followed by flexion and back to extension until the head/helmet stops moving and all energy is absorbed. Movement of the brain is forwards then backwards and then forward again until complete motion of the head is brought to a stop and the brain inside the skull stops moving.

Figure 52: Anterior impact coup-contrecoup injury Figure 53: Side impact coup-contrecoup injury

A force to the side of the head/helmet or to the body which causes the head/helmet to move laterally in a side-to-side motion at the neck produces brain movement in the coronal plane and rotation around the y-axis (Fig. 53). Again, dependent on the movement and amount of lateral flexion at the neck this can cause coup-contrecoup injury to the cerebrum on both sides. The movement of the head in this mechanism is a lateral flexion right to left and left to right until the head/helmet stops moving and all energy is absorbed. Movement of the brain is side-to-side until complete motion of the head is brought to a stop and the brain inside the skull stops moving.

In both of these MOIs the force from impact to elicit a concussion probably has to be greater than forces which cause rotation of the head because the force elicited is only in one axis and one plane of motion. In both of these MOIs the corpus callosum is going to be compressed either from front to back along the y-axis or side-to-side along the x-axis with the possibility of causing damage to it.

Most impacts elicited to the head do not cause the brain inside the skull to move along one axis and through one plane of motion. I think at this point we can agree that most direct and indirect impacts in football do not elicit a straight front to back movement of the head with only flexion/extension at the neck or a side-to-side movement of the head with only lateral flexion to the right and left at the neck. Most impacts cause a combination of these two motions with the addition of lateral rotation of the head. In football most of these impacts are angular in nature and will cause the initial movement of the head into a combination of extension, lateral flexion, and lateral rotation. Angular impacts can cause rotational forces on the brain, which, if severe enough, can result in several rapid changes in velocity (directional speed) over short distances, periods, or both. [68] The head is now moving through three planes and three axes of motion. The previous link from Camirillo best depicts where the rotational motion of the brain caused by angular impacts is most likely located deeper in the brain. The image below shows that the anterior and posterior areas of the corpus callosum are stretched and damaged.

Research has shown that the corpus callosum, a bundle of nerve fibers that carries signals between the brain's left and right hemispheres, is vulnerable to damage from mild traumatic brain injury, commonly known as concussion. [69] These crisscrossing wires can sustain serious damage if the brain suddenly twists or hits against the skull, resulting in mild traumatic brain injury "” otherwise known as a concussion.

Finite Element (FE) simulations found that sagittal rotation of the head has little effect on the corpus callosum. However, coronal and horizontal rotations caused lateral displacement of the falx cerebri at the center and periphery, respectively. (Fig. 54) These motions corresponded with strain in regions of the corpus callosum just below the location of falx displacement, which did not occur when the falx was removed. [70] Although this FE simulation states the strain regions of the corpus callosum did not occur when the falx was removed this statement is not accurate. Removing the falx from a real brain cannot be replicated by FE simulation or computer modeling. Especially when the mechanical and structural function of the falx cerebri is to constrain the brain and limit displacement and rotation inside the cranium. [71] If this is its function how could we say it adds to the damage of the corpus callosum with that same mechanism. The weight of the cerebral hemispheres is causing the stress on the corpus callosum and not the falx cerebri.

Figure 54: Area of damage to corpus callosum in angular impacts

Even though less is known about the impact of damage to the corpus callosum on cognitive function, WITHOUT THE CORPUS CALLOSUM WE WOULD BE EXPERIENCING AN INCREASE AND SEVERITY OF CONCUSSION AND CONCUSSION SYMPTOMS. The corpus callosum provides mechanical and structural support of the cerebrum and absorbs some of the energy and force that would be elicited at the brain stem if it were not there.

In order to see this, we must take a closer look at the anatomy we presented earlier to see why this happens. (Fig. 47) As previously described the corpus callosum is a thick bundle of nerve fibers that connects the left cerebral hemisphere with the right hemisphere allowing communication between them. It is the largest commissural tract in the human brain, with 200-300 million axons connecting the two cerebral hemispheres. [35,37] The corpus callosum is about 10 cm in length and 25 mm in height. [36] My supposition would be that this thick bundle would be more rigid than the surrounding cerebrum as it bridges each hemisphere, and this is supported by research. Myelin is an insulating layer, or sheath that forms around nerves, including those in the brain and spinal cord. Weickenmeier, et al found using a combined mechanical characterization and histological characterization that the white matter stiffness increases linearly with increasing myelin content. [38] Furthermore, modulus of elasticity (elastic modulus) is a quantity that measures a substance's resistance to being deformed elastically when a stress is applied to it, and white matter (corpus callosum) has an elastic modulus which on the average is 39% stiffer than gray matter (cerebrum). [72, 73]

Figure 55. Inferior & Sagittal View of Corpus Callosum

When looking at the placement of the corpus callosum within the brain (Fig. 55) and its composition it is easy to determine that the corpus callosum provides structural support and mechanical stiffness to the brain as a whole. When considering that the cerebrum is 80-85% of the weight of the brain and encircles the brainstem at its attachment site just below the thalamus and above the pons the corpus callosum makes a significant contribution in mitigating concussion caused by brain stem injury. If the corpus callosum was not there to provide structural support to the cerebrum more energy would have to be absorbed by the brainstem and more force would be evoked at the brainstem where the cerebrum attaches via the cerebral peduncles. When you add in the weight of the cerebellum which attaches to the posterior aspect of the brainstem at the level of the pons just below the cerebrum approximately 90% of the weight of the brain is attached to the remaining 10% of the brain which includes the brainstem. This may also answer the question of why we see damage to the corpus callosum in the autopsied brains of individuals who have received the subconcussive impacts to the head in sports and other activities as it is assisting in controlling motion and absorbing energy from the movement of the cerebral hemispheres.

CONCLUSIONS

1. The brain DOES NOT AND CANNOT ACCELERATE ON ITS OWN.

1. The "experts" all agree that it is acceleration/deceleration of the brain that causes sport related concussion. The brain can only be accelerated or decelerated by the acceleration or deceleration of the head/helmet. Therefore, the brain does not accelerate or decelerate at the same time as the head/helmet.

1. The brain is PUSHED back and forth within the skull.

1. The brain cannot bounce, float, or slosh.

1. There is no cerebrospinal fluid (CSF) or space between the dura mater of the brain and the inferior surface of the skull.

1. The brain cannot move in a wave.

1. The structures in the brain have buoyancy, and CSF may flow as a wave throughout the spaces provided by the ventricles, but the entire brain does not move in a wave.

1. The brain is never trying to catch up to the skull because the brain's motion is caused by the movement of the skull.

1. There is NEVER DIRECT CONTACT TO THE BRAIN at the time of a direct impact to the head/helmet or an indirect impact to the body causing whiplash.

1. The first direct contact that occurs to the brain is on the contrecoup side by the inferior surface of the skull after motion to the head/helmet is elicited by a direct or indirect impact.
2. The force exerted to the brain upon direct impact is via the brain's own kinetic energy of motion.

1. Helmets DO NOT ABSORB FORCE TO THE BRAIN.

1. As was pointed out, helmets are designed to reduce acceleration, extend deceleration, and dissipate force. And yes, they do this. But not to the brain, because the brain does not decelerate at the same time as the head/helmet.
2. There is no collision of the brain at the IMPL, as the brain is already next to the inferior surface of the skull. The brain is therefore compressing via its own kinetic energy of motion.

1. The AVERAGE TIME A HELMET IS IN CONTACT UPON AN IMPACT IS 15 MILLISECONDS

1. Helmets are limited in their ability to have effect upon the head and therefore in their ability to protect against SRC.

1. HEAVIER HELMETS INCREASE THE RISK OF SRC AFTER IMPACT.

1. Although I can find no research on the speed of movement of a football helmet after impact the momentum of a heavier football helmet will lead to much greater velocity of the head/helmet and therefore the brain after any impact.

PROTECTING THE BRAIN IN THE FUTURE!

1. A safety system of protection which will protect the brain throughout all the mechanisms which are causing SRC.

1. Protective equipment companies need to begin developing equipment which works with football helmets and shoulder pads to decelerate the head/helmet after all impacts.
2. Smaller and lighter helmets need to be developed for youth football participants within this safety system of protection.

ii. NEEDS TO BE DONE IF WE WANT KIDS TO KEEP PLAYING FOOTBALL.

1. Biomechanical testing and research need to go beyond direct impact in its kinematic measurements of the effectiveness of the football helmet in relation to its protection of SRC.

1. The linear and angular acceleration the head/helmet attains after a direct impact.
2. The velocity the head/helmet attains just prior to whipping to zero velocity after a direct impact.
3. The linear and angular acceleration of the head/helmet on its return toward impact location after whipping to zero velocity.
4. The distance the head/helmet travels reaching zero velocity after initial impact.
5. The total time the head/helmet is in motion after initial impact.

BIBLIOGRAPHY

1. NFL, NFLPA Release 2020 Helmet Laboratory Testing Performance Results. Apr 20, 2020, https://www.nfl.com/playerhealthandsafety/equipment-and-innovation/equipment-testing/nfl-nflpa-release-2020-helmet-laboratory-testing-performance-results
2. NFL, NFLPA Release 2021 Helmet Laboratory Testing Performance Results. Apr 20, 2021, https://www.nfl.com/playerhealthandsafety/resources/press-releases/nfl-nflpa-release-2021-helmet-laboratory-testing-performance-results
3. NFL, NFLPA Release 2022 Helmet Laboratory Testing Performance Results. March 24, 2022, https://operations.nfl.com/updates/the-game/nfl-and-nflpa-release-2022-helmet-testing-performance-results/
4. NFL, NFLPA Release 2023 Helmet Laboratory Testing Performance Results., April 13, 2023, https://operations.nfl.com/updates/the-game/nfl-enters-next-era-of-helmet-safety-with-quarterback-specific-helmet/
5. NFL, NFLPA Release 2024 Helmet Laboratory Testing Performance Results., April 9, 2024, https://www.nfl.com/playerhealthandsafety/equipment-and-innovation/equipment-testing/helmet-laboratory-testing-performance-results
6. Why helmets don't prevent concussions "” and what might. April, 2016, https://www.ted.com/talks/david_camarillo_why_helmets_don_t_prevent_concussions_and_what_might/transcript?subtitle=en
7. What is a Concussion/HEADS UP/CDC Injury Center.

https://www.cdc.gov/headsup/basics/concussion_whatis.html

1. HEAD ANATOMY. https://www.britannica.com/science/head-anatomy
2. Anatomy, Head and Neck, Neck Movements. https://www.ncbi.nlm.nih.gov/books/NBK557555/#

Benjamin Jung; Beenish S. Bhutta. Author Information. Last Update: August 10, 2020.

1. Human Anatomy, 8th Edition. Martini, F. H., Timmons, M. J., Tallitsch, R. B.; Pearson Education, Inc. 2015, Glenview, IL
2. The Size of the Human Brain. https://www.verywellmind.com/how-big-is-the-brain-2794888#
3. Human Brain: Facts, Functions & Anatomy. https://www.livescience.com/29365-human-brain.html; By Tanya Lewis - Staff Writer September 28, 2018
4. Know your brain: Cerebral cortex. December 05, 2014; https://www.neuroscientificallychallenged.com/blog/know-your-brain-cerebral-cortex#:
5. What Does the Brain's Cerebral Cortex Do?; Regina Bailey; Updated February 05, 2020
6. Brain weight: what does it mean?. Clin Neuropathol; Nov-Dec 2003;22(6):263-5. https://pubmed.ncbi.nlm.nih.gov/14672503/#;
7. Chapter 5: Cerebellum.; 5.1 Overview: Functions of the Cerebellum;; James Knierim, Ph.D., Department of Neuroscience, The Johns Hopkins University; Last Review 20 Oct 2020; https://nba.uth.tmc.edu/neuroscience/m/s3/chapter05.html
8. Brain Facts that make you go, "Hmmmmm". https://faculty.washington.edu/chudler/ffacts.html#;
9. Epidural space. https://en.wikipedia.org/wiki/Epidural_space
10. Extradural space Last revised by Deleted User on 25 Mar 2017 https://radiopaedia.org/articles/extradural-space?lang=us#:~:text=The%20extradural%20(epidural)%20space%20is,adherent%20to%20the%20cranial%20bone
11. Anatomy, Head and Neck, Dura Mater. Victor Kekere; Khalid Alsayouri. Last Update: July 29, 2021. https://www.ncbi.nlm.nih.gov/books/NBK545301/#:~:text=The%20meningeal%20layer%20of%20the,cavity%20into%20freely%20communicating%20spaces
12. Subdural space. https://en.wikipedia.org/wiki/Subdural_space#:~:text=The%20subdural%20space%20(or%20subdural,as%20seen%20in%20a%20cadaver
13. Meninges

https://www.mayoclinic.org/diseases-conditions/meningioma/multimedia/meninges/img-20008665#:~:text=Three%20layers%20of%20membranes%20known,is%20called%20the%20dura%20mater

1. Subarachnoid space Last revised by Assoc Prof Craig Hacking◉◈ on 04 Oct 2020 https://radiopaedia.org/articles/subarachnoid-space?lang=us#:~:text=The%20subarachnoid%20space%20is%20the,small%20in%20the%20normal%20brain
2. Anatomy, Head and Neck, Subarachnoid Space Shiza Shafique; Appaji Rayi. Last Update: August 11, 2021 https://www.ncbi.nlm.nih.gov/books/NBK557521/
3. Pia mater. https://www.britannica.com/science/pia-mater
4. PIA MATER - DEFINITION

https://neuroscientificallychallenged.com/glossary/pia-mater#:~:text=the%20innermost%20layer%20of%20the,the%20production%20of%20cerebrospinal%20fluid.

1. In an average adult human, how much distance is between the skull and the brain?. https://www.quora.com/In-an-average-adult-human-how-much-distance-is-between-the-skull-and-the-brain
2. Average distance between the brain and the skull in an adult. https://www.researchgate.net/figure/Average-distance-from-the-brain-surface-to-the-skull-in-each-region-for-the-three_fig6_330818258
3. Cerebrospinal fluid. Production https://en.wikipedia.org/wiki/Cerebrospinal_fluid
4. PHYSIOLOGY OF CSF FORMATION AND FLOW. https://www.uptodate.com/contents/cerebrospinal-fluid-physiology-and-utility-of-an-examination-in-disease-states#
5. Protection of the Brain. https://courses.lumenlearning.com/boundless-ap/chapter/protection-of-the-brain/#:
6. Anatomy, Head and Neck, Dura Mater. Victor Kekere; Khalid Alsayouri. Author Information Last Update: August 10, 2020. https://www.ncbi.nlm.nih.gov/books/NBK545301/
7. An assessment of the role of the falx cerebri and tentorium cerebelli in the cranium of the cat (Felis silvestris catus). Víctor Sellés de Lucas, Hugo Dutel, Susan E. Evans, Flora Gröning, Alana C. Sharp, Peter J. Watson, Michael J. Fagan; 24 October 2018, https://royalsocietypublishing.org/doi/10.1098/rsif.2018.0278
8. Anatomy, Head and Neck, Dura Mater. Victor Kekere; Khalid Alsayouri. Author Information Last Update: August 10, 2020. https://www.ncbi.nlm.nih.gov/books/NBK545301/
9. Ethnicity Influences Corpus Callosum Dimensions. Hilda Nouri Hosseini,1 Mohammad Reza Mohammadi,2 Mohsen Aarabi,3 Narges Mohammadi,4 and Mohammad Jafar Golalipour; https://www.hindawi.com/journals/nri/2018/8916035/
10. Corpus callosum. https://en.wikipedia.org/wiki/Corpus_callosum#
11. Axon position within the corpus callosum determines contralateral cortical projection

Jing Zhou, Yunqing Wen, Liang She, Ya-nan Sui, Lu Liu, Linda J. Richards, and Mu-ming Poo; PNAS July 16, 2013; 110 (29) E2714-E2723; https://doi.org/10.1073/pnas.1310233110

1. Brain stiffens post mortem. J. Weickenmeier,a,b,1 M. Kurt,b,1 E. Ozkaya,b R. de Rooij,a T.C. Ovaert,c R.L. Ehman,d K.Butts Pauly,e and E. Kuhla,*; J Mech Behav Biomed Mater. 2018 Aug; 84: 88"“98.Published online 2018 Apr 22. Doi: 10.1016/j.jmbbm.2018.04.009; https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6751406/
2. Brain stiffness increases with myelin content. J Weickenmeier 1, R de Rooij 1, S Budday 2, P Steinmann 2, T C Ovaert 3, E Kuhl 4 2016 Sep 15;42:265-272. doi: 10.1016/j.actbio.2016.07.040. Epub 2016 Jul 27. https://pubmed.ncbi.nlm.nih.gov/27475531/
3. The Winner of Head Health Challenge III. Published: Sep 06, 2017 at 05:43 AM; https://www.nfl.com/playerhealthandsafety/equipment-and-innovation/innovation-challenges/the-winner-of-head-health-challenge-iii#:~
4. About the NFL HeadHealthTECH Challenge. https://www.nfl.com/playerhealthandsafety/equipment-and-innovation/headhealthtech/headhealthtech-challenges
5. Biomechanics of Concussion David F. Meaney, PhDa,* and Douglas H. Smith, MDb; Clin Sports Med. 2011 Jan; 30(1): 19"“vii. Doi: 10.1016/j.csm.2010.08.009
6. Brain Injury Prediction: Assessing the Combined Probability of Concussion Using Linear and Rotational Head Acceleration. STEVEN ROWSON and STEFAN M. DUMA; Annals of Biomedical Engineering, Vol. 41, No. 5, May 2013
7. Head injury predictors in sports trauma "“ A state-of-the-art review

Fa´bio AO Fernandes and Ricardo J Alves de Sousa; Proc ImechE Part H: J Engineering in Medicine 2015, Vol. 229(8) 592"“608 _ ImechE 2015

1. Head Impact Severity Measures for Evaluating Mild Traumatic Brain Injury Risk Exposure

Richard M. Greenwalda, Joseph T. Gwina, Jeffrey J. Chua, and Joseph J. Criscob

a Simbex, Lebanon, New Hampshire, USA

1. Jadischke, R., Viano, D. C., McCarthy, J. & King, A. I. Concussion with primary impact to the chest and the potential role of neck tension. BMJ Open Sport Exerc Med 4, e000362 (2018)
2. Kuhn, E. N. et al. Youth helmet design in sports with repetitive low- and medium-energy impacts: a systematic review. Sports Eng 20, 29"“40 (2017).
3. 2018 Helmet Laboratory Testing Performance Results. Published: Aug 24, 2018, at 10:28 AM

https://www.nfl.com/playerhealthandsafety/equipment-and-innovation/equipment-testing/2018-helmet-laboratory-testing-performance-results;

1. NFL AND NFLPA RELEASE 2019 HELMET LABORATORY TESTING PERFORMANCE RESULTS. APRIL 12, 2019; https://operations.nfl.com/updates/football-ops/nfl-and-nflpa-release-2019-helmet-laboratory-testing-performance-results/
2. AI Overview. ttps://www.google.com/search?q=wha+kinematics+does+the+nfl+helmet+testing+use&rlz=1C1CHBF_enUS744US744&oq=Wha+kinematics+does+the+NFL+helmet+laborattesting+&gs_lcrp=EgZjaHJvbWUqCQgBECEYChigATIGCAAQRRg5MgkIARAhGAoYoAEyCQgCECEYChigATIJCAMQIRgKGKABMgkIBBAhGAoYoAEyCQgFECEYChigATIHCAYQIRirAtIBCTM1OTQxajBqN6gCALACAA&sourceid=chrome&ie=UTF-8
3. Mechanical Energy. https://en.wikipedia.org/wiki/Mechanical_energy
4. Potential Energy. https://en.wikipedia.org/wiki/Potential_energy
5. Kinetic Energy. https://en.wikipedia.org/wiki/Kinetic_energy
6. Momentum. https://en.wikipedia.org/wiki/Momentum
7. Inertia. https://en.wikipedia.org/wiki/Inertia
8. Coup-Contrecoup Brain Injuries: Symptoms, Definition, and Treatment. Last updated on March 26, 2020; https://www.flintrehab.com/coup-contrecoup-brain-injuries/
9. What is a Coup Contrecoup Brain Injury? Sibley Dolman Gipe Accident Injury Lawyers, PA; June 3, 2021; https://www.dolmanlaw.com/coup-contrecoup-brain-injuries/
10. What Happens in a Coup Contrecoup injury/Concussion Event?. https://www.youtube.com/watch?v=yPCr5yQDOLs
11. How much does your head weigh? https://www.gwosteopathy.co.uk/much-head-weigh/
12. AI OVERVIEW HTTPS://WWW.GOOGLE.COM/SEARCH?Q=ARE+HELMETS+DESIGNED+TO+ABSORB+ENERGY+OR+FORCE&RLZ=1C1CHBF_ENUS744US744&OQ=ARE+HELMETS+DESIGNED+TO+ABSORB+ENERGY+OR+FORCE&GS_LCRP=EGZJAHJVBWUYBGGAEEUYOTIHCAEQIRIGATIHCAIQIRIRAJIHCAMQIRIPATIBCTI0MTAYAJBQN6GCALACAA&SOURCEID=CHROME&IE=UTF-8
13. Whiplash. https://www.dictionary.com/browse/whiplash
14. Skull. https://en.wikipedia.org/wiki/Skull#
15. Theoretical study of the effect of ball properties on impact force in soccer heading. Queen et al (2003) Med Sci Sport Exerc. 35 (12):2069 "“ 2076
16. Concussion in professional football: biomechanics of the struck player. Viano et al (2007) Neurosurg. 61 (2): 313 "“ 327
17. The influence of cervical muscle characteristics on head impact mechanics in football. Schmidt et al (2014) Am J Sports Med. 42 (9): 2056
18. What Happened Within This Player's Skull; By SAM BORDEN, MIKA GRÖNDAHL and JOE WARD; JAN. 9, 2017; https://www.nytimes.com/interactive/2017/01/09/sports/football/what-happened-within-this-players-skull-football-concussions.html
19. Erratum to: Six Degree of Freedom Measurements of Human Mild Traumatic Brain Injury. Fidel Hernandez , Lyndia C Wu , Michael C Yip , Kaveh Laksari , Andrew R Hoffman , Jaime R Lopez , Gerald A Grant , Svein Kleiven , David B Camarillo; Ann Biomed Eng 2016 Mar;44(3):828-9
20. Acceleration-Deceleration Sport-Related Concussion: The Gravity of It All; Jeffrey T. Barth, Jason R. Freeman,* Donna K. Broshek,* and Robert N. Varney" J Athl Train. 2001 Jul-Sep; 36(3): 253"“256.
21. Concussion alters how information is transmitted within the brain; Science News; Radiological Society of North America;
22. https://www.sciencedaily.com/releases/2019/12/191203082910.htm#:
23. Lateral impacts correlate with falx cerebri displacement and corpus callosum trauma in sports"‘related concussions. Fidel Hernandez; Chiara Giordano; Maged Goubran; Sherveen Parivash; Gerald Grant; Michael Zeineh; David Camarillo; Received: 14 June 2018 / Accepted: 5 December 2018 / Published online: 12 March 2019
24. Elastic modulus. https://en.wikipedia.org/wiki/Elastic_modulus
25. Mechanical properties of gray and white matter brain tissue by indentation. Silvia Budday, Richard Nay, Rijk de Rooij, Paul Steinmann, Thomas Wyrobek, Timothy C Ovaert, Ellen Kuhl
26. https://www.google.com/search?q=How+does+a+helmet+cause+a+skid+upon+impact&rlz=1C1CHBF_enUS744US744&oq=How+does+a+helmet+cause+a+skid+upon+impact&gs_lcrp=EgZjaHJvbWUyBggAEEUYOTIHCAEQIRigAdIBCTI3Mjg2ajBqN6gCALACAA&sourceid=chrome&ie=UTF-8
27. https://en.wikipedia.org/wiki/Football_helmet#:~:text=In%201939%2C%20the%20Riddell%20Company%20of%20Chicago%2C,full%20collision%20contact%20occurred%20on%20a%20play.
28. Do helmets protect against concussion? Queensland Brain Institute; https://qbi.uq.edu.au/concussion/do-helmets-protect-against concussion#:~:text=The%20hard%20shell%20spreads%20or,makes%20the%20movement%20less%20abrupt