system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why can't we clench our fists or hold things tightly just after waking up?
gpt
Not a biologist but:

While you sleep deeply your brain releases chemicals that dampen your ability to move (sleep paralysis). 

If you were to wake up in, or close after, a deep sleep cycle this will impact your coordination and muscle control.

Your muscles have not been affected, it is your brains ability to make the muscle work that isn't up to par.