Shoulder pain
 

Hey guys, I've recently changed my strumming/picking method from an open to a closed right hand. It was awkward at first but after a few days I noticed some significant improvement in my picking control, speed, accuracy, etc. the problem is ever since I started playing like this I'm dealing with this tightness and pain in my right shoulder and neck. I'm not sure if I'm not anchoring well enough with my palm on the bridge (used to use a pinky on the pickgaurd) and its causing my shoulder to support all the weight, or if it's something else.
My instructor says it's my big dreadnought and the fact that I'm just playing more than I used to, but I've played a dreadnought for 20 years and I used to play for hours without a problem, so I think it's the closed hand.
Any ideas?

When strumming you shouldn't be anchoring at all, normally. The movement should come from the elbow, swinging the forearm, usually with an additional flick of the wrist. The hand can be open or closed, but it never normally touches the guitar.
Anchoring the hand - either resting the wrist on the bridge, or pinky on the scratchplate - is for more intricate rhythms, or for picking arpeggios, or other fingerstyle techniques: anything where specific strings need to be hit at specific times, rather than all of them at once.

It's hard to see how the problem could simply be caused by the difference between an open and closed hand, unless you've changed your position in some way. If you're playing intricate picking patterns which require anchoring, then it's quite likely that if you're anchoring by resting the wrist on the bridge (instead of pinky on scratchplate), that changes the balance of the arm, and perhaps you've introduced additional tension into your arm and shoulder, as you try to control it. E.g., the forearm and wrist are now fixed in place, in a way they're not if the pinky is the anchor.

Dread guitars give a lot of folks a sore shoulder including me.

I can't wait to see the back of mine. But maybe in your case it is caused by your hand position?

You've got a smaller guitar also, right? Wouldn't playing that and not your dread for a while be a lot more diagnostic than a bunch of guesses from the internet?

Regarding planting your hand on the bridge - I've had teachers (Bryan Sutton for one) discourage all their students from doing that as it robs tone from the guitar. (in case you're interested in getting the best tone possible). Some good pickers do it, though. The best compromise seems to be keeping a floating contact with the fingers on the pickguard &/or thinner strings, when playing on the fatter strings.