Pictorial view of Linear/Rotational
Acceleration here

Rotational (Angular) Acceleration:

This can happen when a player is hit in a fashion which causes the brain to rotate inside the skull. The rotation of the brain can cause shearing of nerve fibers in the brain. This is termed as ‘rotational acceleration’. This form of hit is more typical of a hit to the body, which causes the brain to have a shearing effect. This is caused by a lateral hit to the body, such as an elbow to the head, ball striking the side of the head, kick to the side of the head by a foot, being punched in the side of the head, etc.  Lost of consciousness can occur when the ‘reticular activating system‘ (RAS) is disrupted by movement of the brain.  The RAS system controls the body remaining conscious in life.

This form of acceleration causes more damage to the brain than ‘linear acceleration’, due to the shearing action within the brain, combined with striking the side of the skull.  Brain shearing is medically designated as ‘Diffuse Axonal Injury‘.  Research has shown that blackouts occur more frequently with a rotational acceleration impact to the head/body. For the above picture, the player being struck in the side of the head by the arm is wearing headgear. The headgear in this instance, served no purpose. This is an instance where if a player believes that this form of headgear protects them from all hits to the head, they are mistaken. The hit to the side of the head is below the headband being worn.  More importantly, a hard hit from the side, does not have to involve the head at all, but will cause rotational acceleration factors to affect the brain.  This article, which is regarding a football helmet, speaks of a hit to the side of the body, causing rotational factors to come into play.

The aspects of a hit to a player, resulting in rotational movement of the brain may not be readily seen by spectators as a danger to the head/brain, but just as an impact to the body. The force factor involved causes movement of the brain inside the skull, which is invisible. Damage to the brain is more pronounced from rotational acceleration. A dramatic example of a rotational acceleration hit, and the end result of the player being knocked out, happened in the 2014 World Cup, when a Uruguay player was hit in the side of his head by a knee. The situation was not handled properly by the referees, the team, or FIFA.

The resultant action, with the player going back in to play was a dramatic example of precisely what should NOT be happening on a soccer field. It provided a clear and improper picture to leagues, players, and referees, of how to manage a concussion situation. Since this player had been knocked out, and was obviously wobbly, when walking to the sideline, there was no guess-work needed in this situation.

The end result was that the professional players union, FIFPro, filed an official complaint on the handling of the situation with FIFA, with just reason. It is an extreme irony that FIFA, who is charge of international soccer games, and is the worlds’ largest soccer organization, still appears to be sorely deficient in its’ handling of soccer player health.

Continued examples in the 2014 World Cup clearly portrayed FIFA’s operational deficiency in this area, in front of a world audience. FIFA should focus less in getting perks for FIFA officials, from host countries, and more on the players that play the game.

Linear Acceleration:

When a ‘linear acceleration‘ hit occurs, the head is snapped forward, or backward. This results in the brain striking the skull on the front and rear of the skull (the impact to the front of the skull causes the brain to recoil, striking the rear of the skull). This is not visible to spectators, and the player may be unaware of its’ happening. They may suffer immediate symptoms of the action, depending on the severity of the collision of the skull and brain. This occurs typically from a hit from the front, or the rear, to the body of the player. Understand that a player falling forward, or backward, and striking the ground with their body will cause the brain to collide with both ends of the skull, in a ‘whip-lash’ type effect.

The head does not have to hit the ground, it is the force of the impact with the body that will cause the brain to strike the skull and rebound to the opposite side of the skull, internally. This is a totally invisible occurrence.

When the initial hit to the head occurs, the brain strikes the skull. This is termed a ‘coup‘ blow. The brain rebounds, striking the rear of the skull, which is termed a ‘contrecoup’ blow. The impact factor being determined by the force applied by the hit to the head.

For either linear, or rotational acceleration hits, there may be no immediate signs of problems for the player. The incurred damage to the brain may slowly manifest itself, over a short, or long period of time. This is why experts state that at any point in which an athlete is struck in a manner where a concussions might be possible, that you sit them out and watch them carefully. When removed from play, concussion field tests should be performed on the player, to determine any immediate problems (memory, balance, neuro-cognitive abilities).

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