Lately, I've been noticing my hand cramping up when playing songs with a lot of power chords. The weird thing is, it only occurs when I play the two string power chords, not the ones with the extra octave. I lay my index finger flat when playing them, in order to mute the higher strings.

I get a similar kind of pain when playing barre chords, but only when I press too hard. I always adjust my technique when I feel pain playing those, but no matter how much I adjust myself when playing simple power chords, I keep on getting a cramp. The pain occurs in my palm, that pocket a little bit below the place where the side of your index finger and thumb meet. I'm not sure if I'm explaining this correctly. I'll try to post a picture if you guys need one, but do you have any idea what I could be doing wrong?

I could try playing the octave power chords in most songs, but some call specifically for the simple versions, including ones that I wrote and like how they currently sound. It sucks not being able to play your own songs without crying out in pain.
That's pretty odd. It's normal to get pains on the side of your hand, right below your pinky finger when not accustomed to using that finger a lot, lead playing mostly, or at the center of your hand where your palm creases as you close your hand.

The "pocket" as you say, I have never heard anyone complain about that, so I would recommend seeing a doctor :|

All the best to you, friend
I get this too and have been searching for a way to fix this so if you find one please let me know
id be going to see the doctor, it may not be your technique is wrong maybe you have strained your hand in some way slightly and the constant use of particular muscles in the hand is aggravating it.

like a RSI type thing.

it's not normal to be in pain i wouldn't just brush this away
I'll see about going to a doctor, it won't be for a while as there's some complications with my insurance right now.

I do tend to apply a bit of pressure with my muting, but I always correct it whenever I notice it. I actually have pretty good technique, compared to a lot of players I know. I don't do everything right, though.

When practicing, I either do so standing or playing in classical position, as I'm used to playing classical guitar. I do tend to slouch a bit, I'm not sure if that's really relevant to the pain, but I'll try to catch it whenever I do it.

I could've strained my hand when using improper technique in keyboarding class, as I get a pain when doing that too. Now that I think about it, both of my hands are messed up. I get some pain when writing with my left hand (picking hand).

But yeah, thanks guys. I'll look into seeing a doctor, I may just have to buy a brace and wear that for now.
I had a similar problem when I played a 24.75" scale, because my hands are big. Maybe a using a longer scale length will help you.

Also, if you're playing 2 string power chords, use your pinky finger, instead of your ring finger.
You are probably over doing it. There is a muscle in that area. Maybe it needs a break.
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Just another thing to consider: look at which of the muscles in your hand are doing the work when it comes to fretting; you want the power for fretting to be coming from your fingers and not your thumb. It's kind of a tricky thing to explain but your thumb shouldn't be pressing in to the back of the neck, your fingers should be pressing in to the front.

I very rarely say this but if you experiment for a while you should understand what I mean.

THAT SAID: if you think it's a health issue then definitely consult a doctor, nothing is more important than your health.
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I second go see a doctor. Also, try and get more potassium in your diet.
Washburn MG-44(E)
Ibanez RG421 (Eb)
Art & Lutherie Electric Cutaway
Vox Valvetronix VT40
Vox AC4tv 1x10
Vox Original Wah-Wah Pedal V847-A
MXR '78 Custom Badass Distortion