I was in a car accident a few years ago and got whiplash. This caused severe tightness in the trap muscle (the triangular muscle which connects to the neck, upper spine and shoulder) and pinched nerves throughout this area. It caused numbness and tingling in my arms, hands and fingers. I went through physical therapy and several exercises that helped me to heal tremendously. I previously posted this for someone else who had tendonitis in the shoulder and thought I would repost under another thread for others to benefit.
I haven't been able to find any diagrams online, but I'll try to describe a couple that I know.
1) Sit in a chair with your feet comfortably flat on the floor. Spine straight and arched. Arms hanging down to sides. Bring chin down to chest as tight as you can (make a double chin) and hold for count of 5. If you do this stretch correctly, you should be able to feel it pull from the middle of your next down to your bra strap. Do this for several reps each day (about 10 to start and maybe work your way up to 30).
2) Sit in a chair with your feet comfortably flat on the floor. Spine straight and arched. This should be a chair without arms like a plain kitchen chair and your hands should dangle at just about the seat comfortably while sitting. Grab the chair with one hand and pull your head and neck slowly to the opposite direction until you feel it pull in the side of your neck and your upper shoulder. Hold for a 3-5 count and switch sides.
3) Lie on your back. Legs, arms and spine straight. Tuck your chin as close to your chest as possible without raising your head completely from the floor. Shoulders should remain touching the floor and be square. Hold for 5 count and repeat. This should pull in the same places as #1.
4) Lie on your front on a table or with your face dangling over a pillow so that you can lie face down comfortably. Lift your arms up behind you as if they were wings. If done properly your shoulder blades will crunch together. Hold for 2-5 count and repeat.
5) This stretch requires an exercise band. I don't know where to get them. Mine came from a physical therapist when I was being treated for whip lash. Tie the band to a door knob. Turn your side to the door. Place the elbow of the arm furthest from the door tightly against your ribs. With this same hand grab the band and rotate your upper arm out to stretch against the band. If there is no tension, move further away from the door. During this excercise you should not lift your arm or elbow. Turn it as if the elbow was actually attached to your rib cage and on a swivel. Switch sides and repeat.
6) Use the band in much the same manner in #5 except this time grab the band with the hand closest to the door. Swivel away from the door across your upper body and towards your other arm. Switch and repeat.
7) Stand facing the door and grab the band with either hand while hanging your hand to your side. Then pull your arm straight back until you feel your shoulder blades scrunch together. If the tension is not strong enough, back away from the door until it it. Switch hands and repeat.
These are all great excercises for the neck, shoulder and upper back. They strengthen the trap muscle which controls the tightness or strength in these areas and also controls posture. They worked wonders for my whip lash and when I get tight, I revert back to these excercises to loosen back up. Also sometimes when this muscle gets tight, it will pinch nerves and cause numbness in hands and fingers. These exercises will cure this as well.