Reducing neck and shoulder pain
The chest muscles are often tight and overactive. Its important to stretch out these muscles as part of your exercise plan to improve shoulder position and reduce neck and shoulder pain, including things like tension headaches.
A good exercise for doing this is called "Dumb waiter".
First of all try to encourage these muscles to relax by gently moving the shoulders back and forwards, just by thinking about relaxing the shoulders back. If we take them a little further back then we will feel the muscle between the shoulder blades switch on. I think of this as stage 1 and 2 of Dumb waiter. Then bend the elbows and place them at your sides, palms facing upwards as though holding a tray.
As you breath out start by opening the shoulders and feeling the muscle between the shoulder blades switch on, Then rotate through the shoulders opening up the arms. Try to think of this as a shoulder movement, not an arm movement. You should be feeling a stretch across the chest muscles and some work in the shoulder blade muscles, not a twist in the arms (arms are trying to do too much).
Make sure your elbows are not sliding back and your ribcage is not flaring forward, making the back arch. This is your bodies way of avoiding a stretch into tight muscles. Keep the elbows still at your sides and engage your abdominals to stop the ribs from flaring.