system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What makes holding certain positions, e.g. while lying in bed, more or less comfortable, and why does the degree of comfort eventually change?
gpt
Your body isn't a straight line, and at different times different parts of your body have more pressure on them than others. It takes a small amount of effort to endure that pressure on those points, and over time it adds up and becomes uncomfortable. Shifting positions is basically cycling out which parts of your body are enduring the pressure. More comfortable positions tend to spread out or decrease the pressure on your body, which is why soft things are more comfortable because they do this well.