Balance your workout:
For the most part, remember that people tend to train their push muscles more than their pull muscles. They over-train chest/pecs, and don't do as much lats/rhomboids. This leads to overly short muscles on the front, and internal rotation of the shoulder joint. Posture changes, to a forward lean... and palms face back when standing straight up. (The palms should face in). Try to do equal reps, sets, and weights with the front of your body as you do your back of body. It might take a while to even out!
Rotator Cuff Strengthening:
Warning!: If anything listed below hurts you, stop! Try lowering your weight. If it still hurts, then or after, ice it for 20 minutes, and write me. These are small muscles, with very specific actions. Be precise with your form. Form is everything here, weight is nothing.
Here are the exercises I would recommend:
Supraspinatus/Empty can (See Picture #2):
Weight: 3-10 lb. dumbbell. Don't push this- it's a tiny muscle. I use 5.
Reps: 2 sets of 12
Form: Stand with a dumbbell in each hand. Do one arm at a time. Raise your stiff arm in front, up away from your body to shoulder height, no further. Rotate the hand inward until you are in a thumb down position. In that thumb down position, lower the weight until your thumb hits your thigh. Raise it, never above the shoulder level. Move slowly. Note Picture #2, in the picture on the right, the shoulder is down and away from the ear. That is correct form. In the picture on the left, the shoulder is "scrunched" up to the ear. That's not correct.
Do 12 reps. Do the other arm, and repeat both.
Subscapularis (See Picture #3):
Weight: 10-40 lbs. Form is important here, so try it light first. I do 30 lbs. with a "healthy" shoulder.
Reps: 2 sets of 12
Machine: Set a cable pulley machine so the handle is at shoulder level. Use a D ring handle.
Form: Your back is to the machine. Grab the handle with a stiff arm. Raise the stiff arm out in front of you. The cable should run under your arm pit. The arm should be in the up position of the previous exercise, only palm down. Elbow locked, hand out at shoulder level. Hold your body and trunk stiff. Now translate ONLY your shoulder forward. Of course the arm and hand will move to, but it's just a shift forward, leaving the rest of your body still. Don't rotate your trunk. Your scapula will track along your ribcage, and your humeral head will push forward. You should feel this only lightly in under your armpit, actually in the front (anterior) surface of your scapula (shoulder blade).
External rotators - teres minor and infraspinatus (See Picture #4):
Note: This is described and shown in the picture below for the left shoulder, but you should do all of these on both shoulders. You can then do the same thing on the other shoulder. Weight: 5-10 lbs. I use 15 when my shoulder feels good, less when it doesn't.
Reps: 2 sets of 12. Do Right arm, then left, and repeat.
Machine: Set cable pulley machine so the pulley and handle is at elbow height. Set your weight. This exercise can irritate, so better to err on the light side then the heavy. Use a D ring handle.
Form: Stand with your right shoulder to the machine, your left shoulder away. Hold the handle in your left hand with palm facing the machine, elbow bent to 90 degrees. Glue your elbow to your ribcage. Keep your shoulder down and away from your ear. The inside of your forearm should be on your belly to start with. Move away from the machine until the slack is taken out of the cable. Now externally rotate your left upper arm, lifting the weight until your knuckles point straight ahead, now go a little further. Don't force it into external rotation, it will hurt you. Lower the weight. Do 12 and go do the other arm, and repeat both.
Internal Rotators - pec. minor and subscapularis (See Picture # 5):
Note: This too is described for the right shoulder. You should do all of these on both shoulders also. But, this is only going to be described this way.
Reps: 2 sets of 12
Weight: internal rotators are stronger and less vulnerable than externals, so I go a little heavier... 20-30 lbs. for a guy... I use 20 when I feel good, and less when I don't. Know yourself.
Machine: Leave machine in the same position as last exercise. Turn around so your right shoulder is to the machine. Glue your elbow to your ribcage. Keep your shoulder down away from your ear. Bend your elbow to 90 degrees, knuckles pointing forward, and palm facing away from the machine. Step away from the machine to take the slack out of the cable. Rotate upper arm in to lift weight until the inside of the forearm is on your belly. Return the weight to almost touching the stack. Again, do not allow external rotation to the point of discomfort. Repeat 12 times. Do the other arm. Do both again.