Originally Posted by: tracy mcconkeyso i am still pressing hard on the back of the guitar with my thumb - causing both muscle and joint pain.

Ok, I've been through the whole deal... pain, then numbness, carpal tunnel, then recovery and back to playing. All the advice given so far is good, some things may help more than others.

First off, I don't think you have carpal tunnel syndrome. When you get that, its not a pain you can play through. You tend to get numb fingers, loss of dexterity, and severe pain with very specific types of movement. To me, it sounds like you're just getting normal pain associated with stressed muscles and joints. Before you go too nuts trying to figure out the problem, here are a couple of things to try that may help immediately:

1) Relax your fretting hand, don't press so hard. You can work on this by taking your thumb away from the fretboard, and then seeing if you can still fret notes and chords. So just go ahead, try to fret a note or chord, with your thumb totally out of there... start by making a gentle fist with your fretting hand (I assume its the left hand)... turn your hand towards you, so your palm is up (still making a fist). Now, open up your thumb like you're trying to hitch a ride. Now open up your fingers, and place them on the fretboard to fret a chord or notes, keeping your thumb relaxed in the same position away from the back of the fretboard. Try to see if you can fret cleanly... takes a little practice, but depending on your guitar, you should be able to do it... All you're trying to do here is see how little pressure you can use to still play the notes & chords properly... you don't need a death grip on the guitar. Go ahead and use your thumb for support now, but try to keep the pressure at a minimum.

2) Some players find it much more comfortable to hook their thumb around the fretboard, so that the back of the neck sits more in their palm rather than having their thumb placed directly on the back neck. Watch both electric and acoustic players on YouTube, and you'll see this is a very common way of holding the neck regardless of music style. Its not a bad idea. Your thumb was not meant to be pushed backwards, so putting a lot of pressure on it as you play can easily cause the kinds of problems you're having. When I'm playing guitar, most of the time I use the "palm/thumb wrap" position when I fretting, and then slide my thumb directly behind the fretboard into the more "classical" position only when I have to in order to play cleanly. So if I were strumming open chords for example, I would pretty much always be using the palm/thumb wrap technique. That, combined with using only as much pressure as needed to fret chords and notes cleanly, allows me to play comfortably for long periods of time.

Hope this helps!

Cal