system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5: Why is grip strength significantly worse when you first wake up? And why do hands feel so stiff in the morning?
gpt
When you sleep, your body turns turns off a lot of movement circuits so you don't act out everything you're dreaming. These may take a while to turn back on when you wake up, varying between people and which stage of sleep you woke up from (as others have pointed out, called 'sleep inertia').