SPORT-RELATED CONCUSSION (SRC): What happens inside the skull?

SRC is a traumatic brain injury induced by biomechanical forces; it may be caused either by a direct blow to the head, face, neck or elsewhere on the body with an impulsive force transmitted to the head. [1] To simplify, SRC in football occurs from direct impact that causes contact and inertial forces to the head and from indirect impact that causes only inertial forces to the head. A direct impact to the head/helmet causing the head/helmet to decelerate and accelerate can occur with helmet-to-helmet, helmet-to-shoulder pad, helmet-to-body, or helmet-to-ground forces. An indirect impact is caused when there is no contact with the helmet, but the head/helmet moves suddenly or violently.  This can occur with body-to-body impacts causing the head to change direction rapidly. In both cases of direct or indirect impacts, the point of emphasis is that THE HEAD MOVES in the majority of impacts in football. Most experts agree that abrupt acceleration/deceleration of the head is the cause of SRC. But the question to be asked in the prevention of SRC is “What is happening to the brain during acceleration/deceleration of the head?” 



If you are following my posts, we learned last week, that based on the structural anatomy of the brain, it is separate from the skull and does not bounce. If the brain does not bounce (even though many are taught that it does), then what does the brain do? One mechanism of direct contact is helmet-to-helmet in which both move with velocity and direction. During contact each helmet comes to zero velocity prior to changing direction and then they accelerate away from each other and reach a new velocity based on their momentum. Does the brain reach zero velocity at the same time as the helmet? Of course not! It is separate from the skull. The brain is still accelerating in the direction of the contact because it is separate from the head/helmet. The part of the brain closest to the point of contact moves into the skull first as the back side compresses. The brain does not begin to decelerate and reach zero velocity at the same time as the head/helmet. It continues in the same direction until the head/helmet changes direction and begins pushing the brain in the opposite direction of contact. The energy that is elicited to the brain is not from the contact, but from its own kinetic energy of motion toward contact site. This push of the brain by the head/helmet continues until the entire brain’s momentum is moving in the same direction as the head/helmet. Important to note: Deceleration of the head/helmet to zero velocity on contact occurs while acceleration of the brain inside the skull continues. One is slowing down, and the other is not. 


What happens next? The head/helmet continues to accelerate moving away from the contact pushing the brain until the head/helmet whips to a stop coming to zero velocity.  When the head/helmet stops moving, the brain is now accelerating with its own momentum inside the skull. The brain separates from the contact side of the skull and continues in motion with its own velocity in the direction the head/helmet reached its zero velocity. As this motion of the brain occurs, the head/helmet begins accelerating back towards the contact site and hits the brain pushing it in the opposite direction. This continues to occur until the head/helmet stops moving. Important to note: During this second contact of the brain with the skull, the brain is accelerating in opposition to the acceleration of the head/helmet. They are in motion and accelerating toward each other. 


All of the mechanisms of injury are what we call SRC, and they occur in less than a second. The head/helmet stops moving in less than a second in most incidences. Does the SRC occur with the first contact of the skull and brain or the second contact? Or do both contribute to the SRC? Based on our previous post about the narrative created by helmet companies and the NFL, it only occurs on the first contact between the skull and brain as the helmet only works during direct contact.


I believe that injury to the brain (SRC) undoubtedly occurs with both the first and second contact of the skull and brain. One could even make the argument that even more force elicited to the brain on the second contact of brain and skull than the first. Here’s why! When a player is setting up to block his opponent on a kickoff return and they hit helmet-to-helmet, the blocker is usually the player who sustains a concussion. The blocker’s head/helmet has very minimal motion and velocity upon contact with the opposing player’s helmet. For all practical purposes, the head/helmet and brain of player blocking on the kickoff are not moving when struck by opponent covering the kick. Therefore, both head/helmet and brain are basically at zero velocity when contact occurs. The direct impact causes the blocker’s head/helmet to move, and the inferior side of the skull pushes the brain in the direction the head/helmet is moving after contact. Important to note: In this first contact of skull to brain the head/helmet is accelerating into the brain which is fairly stationary with little or no acceleration or deceleration.  The head/helmet accelerates based on the momentum created by impact and begins pushing the brain. The mass of the head/helmet is 12-13 pounds; it is pushing a 3-pound brain. [2.3] When the head/helmet comes to zero velocity as it whips to a stop the brain is now no longer in contact with the skull and its momentum and acceleration is less than the head/helmet. As the head/helmet comes out of zero velocity, it changes direction and moves back toward the brain, striking the brain which is still moving in the direction the head was moving prior to its change of direction. Important to note: The head/helmet and brain are accelerating toward each other. 


Back to the question of does the SRC occur with the first contact of the skull and brain or the second contact? Or do both contribute to the SRC? I believe it is very clear that there are forces elicited to the brain after direct impacts to the helmet that attribute to SRC. It is also apparent that the brain is not bouncing back and forth inside our skulls but is being pushed back and forth by the momentum of the head/helmet after direct impact. Therefore, it is important to understand that movement and speed of motion of the head/helmet after direct impact significantly increases the chance that a SRC can occur. Which is why technology going beyond the helmet is necessary to prevent SRC. The necessary innovation must decelerate the head/helmet after impact.


More support for this necessary technology will come in my next blog which addresses SRC caused by indirect impacts. 

Helmets protect heads. Kato Collar protects brains!

  1. Consensus statement on concussion in sport—the 5th international conference on concussion in sport held in Berlin, October 2016; McCrory P, etal; Downloaded from on January 2, 2018 – Published by;
  2. The Size of the Human Brain.
  3. Human Brain: Facts, Functions & Anatomy.; By Tanya Lewis – Staff Writer September 28, 2018

Sport-related Concussion (SRC): Brains Don’t Bounce!

Helmet companies want us to believe the brain bounces back and forth after impact that is what causes a SRC. And the NFL has coined the term HeadHealth having us believe the term means they are addressing the brain and SRC. Neither are the whole truth!   The brain does not bounce and HeadHealth does not always address brain health.  In order to better understand this, we need to review the structural anatomy of the brain. It is absolutely crucial to understand that the brain is separate from the skull. When the literature regarding the mechanism of injury for sport related concussion talks about the head, in most instances, they are referring to the brain and the skull as one unit. But when defined by 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 brain might be contained in the skull, but the brain and head are two separate entities. You can move your head, and your head moves your brain. You cannot move your brain inside your skull.

The best way to see this is through a picture of how the brain is housed inside the skull.

The theories we have been led to believe about how the brain moves in a concussion I will call the “Bouncing Brain Theory” and the “Floating Brain Theory”. From Figure 1 and 2 above you can see the different layers and spaces between the skull and the cerebrum which lies just below the pia mater. In most pictures like this the cerebrum is labeled the brain (as in Fig. 1) which can be confusing when talking about a SRC because everything below the skull is part of the brain and includes the dura mater which lies directly next to the inferior side of the skull . .  Pictures like this also make us think there is a significant distance between the skull and the cerebrum and other structures of the brain. When in reality the space between the inferior skull to the cerebrum or other parts depending on the location is only .4 and 7 mm which is extremely small.[1] Most of the cerebrospinal (CSF) fluid lies in the subarachnoid space which leads to why we are made to think that the brain bounces or floats. These two facts: 1) the brain is separate from the skull; and 2) it is packed inside very tightly should make it easy to deduce that the brain cannot bounce back and forth. But there is other anatomy of the brain which also keeps the brain from bouncing or floating.

In addition to this, CSF and the ventricles contained within the brain integrate with the CSF contained in the spaces between the linings so that the CSF flows in a system designed to protect the structures of the brain enclosed by the skull (Fig. 3).

The ventricular system consists of four ventricles within the brain which do provide some buoyancy to the brain in order support and protect structures, but not enough to make it float around inside the skull. CSF surrounding the brain combined with flowing through the four ventricles and folds protect the brain by acting as a shock absorber and supporting the brain through suspension by providing buoyancy. [2,3]

And then you incorporate the corpus callosum into the mix which is the largest commissural tract in the human brain, with 200-300 million axons connecting the two cerebral hemispheres. [4,5] The corpus callosum (Fig. 4) is a thick bundle of myelinated nerve fibers 10 cm long and 25 mm high made up of white matter. [6] White matter has a higher elastic modulus than gray matter and myelination of nerves increases this modulus of elasticity. [7]  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). [8,9] So not only  is the corpus callosum’s function to connect the two cerebral hemispheres for communication but based on its histological make up it is a supportive structure of the cerebrum during excessive motion caused by forces acting on the brain from the different impacts causing SRC.

Based on the brain’s mechanical and structural anatomy designed to absorb the kinetic energy created by its  own movement in reaction to impacts causing violent movement of the head the brain is not bouncing back and forth inside the skull as depicted in the movie “Concussion”.  The brain’s motion is always and only in reaction to the movements of the head. The head initiates all movement and contact of the brain that causes a SRC. 

My next blog will explain the types of impacts and the mechanisms of injury which cause SRC. 

Helmets protect heads. Kato Collar protects brains!

  1. In an average adult human, how much distance is between the skull and the brain?.
  2. Human Anatomy, 8th Edition. Martini, F. H., Timmons, M. J., Tallitsch, R. B.; Pearson Education, Inc. 2015, Glenview, IL
  3. Protection of the Brain.
  4. Ethnicity Influences Corpus Callosum Dimensions. Hilda Nouri Hosseini,1 Mohammad Reza Mohammadi,2 Mohsen Aarabi,3 Narges Mohammadi,4 and Mohammad Jafar Golalipour;
  5. 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;
  6. Corpus callosum.
  7. Brain stiffness increases with myelin content. J Weickenmeier 1R de Rooij 1S Budday 2P Steinmann 2T C Ovaert 3E Kuhl 4  2016 Sep 15;42:265-272. doi: 10.1016/j.actbio.2016.07.040. Epub 2016 Jul 27.
  8. Elastic modulus.
  9. Mechanical properties of gray and white matter brain tissue by indentation. Silvia BuddayRichard NayRijk de RooijPaul SteinmannThomas WyrobekTimothy C OvaertEllen Kuhl

Sport-Related Concussion (SRC): What Will You Do With The Truth?

The prevention of concussion in sport is not what we have been taught to believe!

In April 2020, VICIS, a football helmet company who spent millions of dollars and was at one time valued at $90 million, who introduced their football helmet in 2017, sold to another football helmet company for $2.85 million.[1] When I read this, I questioned how we have been led to believe that a football helmet is the only available protective safety equipment with the technology capable of preventing sport-related concussion (SRC). Because this is what they want us to believe! And indirectly, the NFL has supported and even promoted this narrative and paradigm of thought. 


The helmet companies have created a narrative that concussions only occur with direct contact to the helmet through the biomechanical testing of helmets. The majority of testing on helmets have focused on the kinematic measures of peak linear acceleration (PLA), peak rotational acceleration (PRA), impact duration (IMPD), and recently impact location (IMPL) has been incorporated into the mix. [2,3,4,5,6,7] It is important to note that IMPD is a key factor here as these measures are only taken during impact. The IMPD of the head/helmet is the time period when the head/helmet collides with another body. Head/helmet impacts have been recorded as having an IMPD between 5.5 and 13.7 milliseconds (ms). [8] In some way the head is still moving after impact. Therefore, the brain is moving and vulnerable for much longer than the IMPD. Intentional or unintentional the paradigm of thought is they want us to believe is that helmets protect the brain. Which is simply not the whole truth. The brain is at risk for SRC as long the head continues to move which is much longer than milliseconds. If helmets only protect during IMPD does other technology need to be investigated to protect the brain after impact?


Again, whether it is intentional or unintentional the NFL indirectly promotes and supports the narrative that helmets are the only technology available to prevent SRC. On April 20, 2021, the NFL and NFLPA released its 2021 Helmet Laboratory Testing Results ranking the VICIS ZERO2-R MATRIX, VICIS ZERO2-R TRENCH, and the VICIS ZERO2-R helmets as best performing helmets in their laboratory research tests.[9] On the same day the NFL and NFLPA released their laboratory testing results they also approved the first position-specific helmet design for offensive and defensive lineman, the VICIS ZERO2-R TRENCH. [10] And with the release of the 2021 results, Jeff Miller, NFL Executive Vice President overseeing Player Health and Safety, offered a $1 million prize for a winning helmet which improves on the performance score achieved by current top-performing helmets by more than 15%. This would mark a transformational improvement approximately five times greater than the average year.[9] As a health care professional and a consumer this raises several questions. How can the number one ranked helmet by the NFL basically go out of business if a helmet protects against concussion? And what is a 15% improvement in the performance of a helmet when we have not been informed of the % improvement in helmets over the past 10-12 years? If a 15% improvement is what is sought, then past improvements have occurred in very minimal increments.


This picture that has been painted by the helmet companies and the NFL is that the helmet is the only way to protect the brain. This is not the whole truth and believe it or not they know it! Want to know more? 



1  Innovatus Capital Partners Buys Remaining VICIS Assets.;

Andrew Cohen; April 13, 2020

2  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

3  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

4  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

Concussion with primary impact to the chest and the potential role of neck tension. BMJ Open Sport Exerc Med 4, e000362 (2018)

Jadischke, R., Viano, D. C., McCarthy, J. & King, A. I.

6  Youth helmet design in sports with repetitive low- and medium-energy impacts: a systematic review.  Sports Eng 20, 29–40 (2017).  Kuhn, E. N. et al. 

 7  Comparison of Impact Performance between Youth and Varsity Football Helmets. Proceedings of the ImechE 231, 374–380 (2017).  Sproule, D. W. & Rowson, S.

8  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

9  NFL, NFLPA Release 2021 Helmet Laboratory Testing Performance ResultsPublished: Apr 20, 2021 at 01:56 PM;

10  FL, Players Association approve first position-specific helmet design for OL, DL; By Kevin Seifert; April 20, 2021, 2:09 PM