system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why can't I form a tight fist with my hands straight after waking up?

For some reason, no one can create a tight fist just after waking up. Is it something to do with muscles being too relaxed?
gpt
It has to do with muscle relaxation and neurotransmitters during the sleep cycle. In certain stages of sleep, your brain tells all the **skeletal** muscles in your body to relax, and become "un-tense". (Skeletal muscles are the ones you control). Depending on which stage you might wake up in, you could have difficulty clenching your fists (or balancing yourself if you stand up as soon as you wake).