system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do our bodies find certain positions comfortable at night.
gpt
We get the urge to shift our sleeping position almost entirely to prevent blood from pooling. It is an innate thing.

People are bedridden and don't shift around, like those in a coma, can get bruising or even terrible ulcers if not cared for properly. These are bedsores. In the worst case scenario you can lose a limb to them.