Concussive Blow vs Sub-Concussive Blow – Which is More Dangerous?

Dr. Robert Cantu, the prominent neurosurgeon out of Boston and undisputed concussion expert, has stated that a lineman in the NFL, on one 80 yard drive, can sustain up to 18 sub-concussive blows. 18! 15,000 in a ten year NFL career!

With that in mind what is more dangerous to the athletes – Concussive Blows or Sub-Concussive Blows?

Michael Felder, who is the national college football lead writer for the Bleacher Report covered a debate titled “To Ban or not Ban College Football”. He wrote a very interesting article titled- Sub-Concussive Blows Are the True Danger in College Football. The following is an excerpt from that article.

“While there were a lot of interesting takes, the part of the debate that got washed over was likely the most critical to understanding the dangers of football. Malcolm Gladwell made the astute point that concussions are merely a small part of the problem. Overall, the head injuries that people should be concerned about are the day-to-day, run-of-the-mill, repetitive blows to the head that most people do not even notice.

You see, concussions are the massive brain traumas. They result in your favorite athlete being knocked out, staggering, becoming dizzy, having headaches, vomiting and what have you. College football is doing a great job of identifying these blows and parking those players on the bench, taking their helmets and ensuring that they do not return to the game or to practice until all of the symptoms are gone.

The more I read about Chronic Traumatic Encephalopathy, the less these big concussions scare me. Those get handled correctly. It is the continuous small blows to the brain that are creating the damning evidence being found in the brains of former football players.
CTE, as it is called, is not the product of massive concussions, rather it is borne through repetitive sub-concussive blows.

Those little hits. The constant banging on the offensive and defensive line. The running back being tackled every play as he carries the ball over 200 times a season. The linebacker who is putting up 125 tackles. Those are not all concussions, but they are repetitive sub-concussive blows to the head that are the building blocks of CTE.”

David Hovda, PhD at UCLA gives us a very detailed explanation as to what is happening to the brain at the cellular level during and after a concussive blow as reported by John Doherty.


“When there is a sufficient blow to the brain, the membranes of the affected nerve cells in the brain are stretched or twisted, allowing potassium to exit those cells, which triggers those cells to depolarize, thus the phenomenon of seeing stars if the affected area is involved with sight or ringing in the ears if the affected area is involved with hearing. The exit of potassium (K+) peaks approximately two minutes after the incident but continues for another 3-4 minutes.

Then, until the chemical balance is somewhat restored, those neurons (nerve cells) are unable to fire again. Furthermore, in a protective reflex of sorts, surrounding cells begin to shut down, a process Hovda calls “spreading depression.”

If enough cells become depressed, confusion, amnesia, and even loss of consciousness result.
Meanwhile, in an attempt to recover, the brain starts using up massive amounts of blood sugar and will continue to do so for as long as 30 minutes. This overuse of this glucose results in the production of lactic acid which, in excess amounts, inhibits brain function.

A demand for glucose by the brain, such as when one is studying, logically causes an increase in blood flow to the brain. However for reasons not entirely clear, within two minutes of a concussion, the body decreases blood flow to the brain by up to 50 percent. This process continues unabated for 3-4 days but fully normal blood flow may not resume until an average of 10 days have passed. Consequently, at precisely the time the brain needs extra fuel to repair itself, it ends up getting less.

Meanwhile, the exit of potassium allows calcium to enter the neuron. And while the exit of potassium ceases in minutes, it takes the cell 2-4 days to rid itself of the energy-inhibiting calcium.

While the immediate chemical reaction of the brain to the concussion is brief and generally completed in 30 minutes, it takes days for the individual cell and the brain as a whole to restore that chemical balance which was lost so quickly. Until that balance is restored, the brain doesn’t work as well and is particularly vulnerable to re-injury.

Sub-Concussive blows are clearly more dangerous. Why? Athletes play through them and get even more hits when the brain is most vulnerable.

Sub-concussive blows are easier to prevent than a full on concussion. A strong force dissipating neck cylinder will dissipate the lessor hits that would cause a sub-concussive blow and protect the brain from CTE.

Dr. Cantu has also pointed out that 85% of concussions and sub-concussive blows happen from rotary acceleration to the head. Picture a football helmet. When two helmets collide it will always create rotary acceleration as they glance off each other. We must build force dissipating strength in our athletes necks. They will come back and thank you later in life.

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