Fragile bodily positions

Fragile positions include lying on your back, sitting down?

Fragile in so far much as insecure; when you’re lying on your back, you’re in an inferior, dangerous position. For example in the UFC, or mixed martial arts, to be thrown down and on your back, just like a roach or something on its back; a rhino on its back is not a good position to be in. We cannot imagine a gorilla, a dragon, or anything lying on its back; it is a position of submission? Like someone lying down legs spread in a missionary position?