Immediately after moderate forces have been applied to the brainstem, the forearms are held flexed or extended (typically into the air) for a period lasting up to several seconds after the impact.
Tonic posturing preceding convulsion has been observed in sports injuries at the moment of impact[2][3] where extension and flexion of opposite arms occur despite body position or gravity.
[citation needed] In simpler terms, the shock of the trauma manually activates the nerves that control the muscle groups responsible for raising the arm.
Likewise, animal models of diffuse brain injury have illustrated a fencing response upon injury at moderate but not mild levels of severity as well as a correlation between fencing, blood–brain barrier disruption, and nuclear shrinkage within the LVN,[4] all of which indicate diagnostic utility of the response.
As a result, greater emphasis has regularly been placed on the management of concussions in athletes than on the immediate identification and treatment of such an injury.