Fragile bodily positions

Fragile positions include lying on your back, sitting down?

Fragile in so far much as insecure; when youโ€™re lying on your back, youโ€™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?