system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is sitting/standing straight so uncomfortable? Conversely, why is slouching or other weird postures feel so comfortable?
gpt
It's a mix. First, slouching is most of the muscles used to maintain posture relaxing. It naturally feels more relieving for those muscles to not have to work. Like how most of the time sitting feels better than standing, it's essentially letting a group of muscles rest.

Second is that unless you have a solid habit built for good posture, you have to think about maintaining it. You randomly find yourself slouching and have to change it. Thinking and adjusting how your body just naturally exists is uncomfortable.