To prostrate, as Collins dictionary says, means:
"If you prostrate yourself, you lie down flat on the ground, on your front, usually to show respect for God or a person in authority"
On the other hand, when we refer to the prostration done by people of some religious communities, we often picture a slightly different position (see pictures below).
Clearly, in these pictures, the body is not lying down flat on the ground but curled up. So, the questions are:
- If, without any context, I just say that a man prostrated himself on the ground, what prostration would you picture?
- If, as Collins dictionary says, a prostration generally refers to a flat position, how would you describe the specific type of prostration shown in the pictures (without mentioning this or that specific religious community or term)?
Addendum: I found this description of a work of art that says "two men are kneeling prostrate before a statue". The picture is quite dark, but the two men looked in the same position as the one described here. It's from the British Museum by the way, so it should be reliable. What do you think of it?
Second addendum: This ngram search tells us that probably "to be prostrate on one's knees" is even more used. So, for instance, "He was prostrate on his knees".