DeSean Jackson is helped off the field after a vicious hit to the head. The hit resulted in his second concussion in two years. (Photo by Al Bello/Getty Images)

Earlier this week, the league levied steep fines for several violent hits delivered by players either as helmet-to-helmet contact or hitting defenseless receivers.  The primary issue is the threat of concussion, an injury to the brain that can result in the loss of memory, reduced cognitive ability, and an inability to speak normally.  In severe or repeated cases, concussions can cause ongoing headaches, change one’s personality, and accelerate the onset of Alzheimer’s disease.

Mechanically, a concussion takes place when the brain strikes the inside of the skull through some sort of traumatic force.  Think of the brain as a loosely-belted passenger in a car, and recall Newton’s first and second laws of physics.  If the car is driving straight ahead and crashes into a brick wall, the passenger will continue moving ahead at the previous speed until the belt or the dashboard stops him.  Similarly, in a head-on helmet-to-helmet hit, the brain crashes into the front of the skull, potentially causing temporary or long-term damage.  When you consider how the game is played and the sense of invincibility that players likely feel with helmets and pads, it’s a wonder that concussions aren’t suffered on every play.

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