Hello, I'm having trouble play the power chords for a shorter( :p ) amount of time. After a couple of minutes i can barley move my hand for some reason, it doesnt really hurt, but my whole lower arm gets really stiff, is this usual?
Hello and welcome

I'm far from an expert, but it sounds to me like the muscles in your forearm are fatiguing or cramping up....
I don't know if you are aware that the muscles that work your fingers are all up in your forearm, rather than in your hand.
It might be happening because these finger muscles haven't yet developed the strength to hold the chord down for any length of time. I would say this is fairly normal, and will pass as you build strength in the right places.
It might also happen because:
Your muscles aren't warmed up - start with something gentle;
You are applying much more pressure than necessary (the death grip) - Try relaxing your grip until you reach the minimum you need to play the chord cleanly, then be careful not to let tension creep back in.
Your wrist might be at an awkward angle - have a look at yourself playing in a mirror to check.
You may have some medical condition that we don't know about !

- if it gets painful, or doesn't show signs of improving, then go and see your doctor.
My guess would be that you just need to build up finger strength. How long have you been practicing barre or power chords for?
Andy