The Fencing Response

During the first few years, human babies display interesting reflex actions. One such reflex action is the moro reflex. That is, when a baby’s head is lifted a few inches up and then is dropped, the baby extends its arms outwards as if trying to find a support and is reaching out to stabilize itself. Here’s a video of a baby’s moro reflex.

When the baby grows, this response usually goes away because the brain starts to learn to suppress reflexes. But they sometimes still do appear. For instance in the case of a minor head injury – usually during sporting events. In this case, even adults can reactivate the infantile reflex due to a trauma to the brain stem. When this happens the person extends his arm in a peculiar position – like the “en guarde” position – and falls down. Wikipedia describes it as:

The fencing response is a peculiar position of the arms following a concussion. 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. The fencing response is often observed during athletic competition involving contact, such as American football, hockey, rugby and martial arts.

Here’s a video compilation of players in sporting events falling down with a fencing response after an injury to their head. This of course is rare, but when it does happen, a referee is trained to stop the play because it is an overt indicator of serious injury to the head. It’s nice to know and it will be fun to notice this in the upcoming superball.

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