Need help with translating a sentence


The sentence is:

> 俯伏{うつぶ}しに延｛の｝び切｛き｝った身体｛からだ｝を縮｛ちぢ｝めて一寸{ちょっと}腰｛こし｝の所｛ところ｝を高｛たか｝くした。

For context, this is a short story by Naoya Shiga, the name is 「十一月三日午後の事」.
Right before this sentence, the subject of this sentence trips and falls face
down and is very exhausted. He has someone trying to help him up, and he is
trying to get up as well.

I know the meanings of the words individually or the probable meaning for
those that have more than one, however, I'm unable to picture what the author
is trying to say.

Later on, the author describes this action as

> 芝居{しばい}で殺｛ころ｝された奴｛やつ｝が俯伏｛うつぶ｝しになった場合｛ばあい｝よくそう云｛い｝う動作｛どうさ｝をする。

I took this to mean "In a play, when the guy who gets killed is lying face
down, he often does this action."

However, I still can't put together what the author means.




ちょっと腰のところを高くする ("to elevate one's hip/pelvis a bit") from the うつ伏しにのびきった
("flat prone") position should look like this:

[![身体を縮めて一寸腰の所を高く](https://i.stack.imgur.com/rWorMm.png)](https://i.stack.imgur.com/rWorMm.png)

In a movie cut scene, we often see a dying person who doesn't have enough
energy to stand or sit does this.




ちょっと腰のところを高くする ("to elevate one's hip/pelvis a bit") from the うつ伏しにのびきった
("flat prone") position should look like this:

[![身体を縮めて一寸腰の所を高く](https://i.stack.imgur.com/rWorMm.png)](https://i.stack.imgur.com/rWorMm.png)

In a movie cut scene, we often see a dying person who doesn't have enough
energy to stand or sit does this.

