The key on working the RC's is to use very light weight with high reps. By light weight I mean starting off/warming up with 5 lb. DB's, and maybe working your way up to a 10 Lb. DB until you build some strength. I do rear delts whenever I do shoulders and I do RC's maybe 1-2 times per week. The key when working your RC's is to NEVER do them before you do chest or shoulder exercises. Pre-exhausing your RC's is not a good idea. If you do them on a chest or shoulder day, do them after your normal workout. I'll list some of the exercises I do for each:
FOR REAR DELTS:
1) Rear flyes using either a pec deck machine or using light DB's (10 Lbs.). When I use DB's, I typically lie on my stomach on an incline bench and just do reverse flyes. Make sure you do some sets with your palms facing down, do some sets with your wrist slightly turned so that your thumbs face up toward the ceiling, and do some with your thumbs facing down toward the floor. By rotating your wrists with your thumbs down and up, you will also hit your teres minor and infraspinatus, which are 2 of the 4 RC muscles.
2) Bent over flyes. Same motion as above, just do them standing bent over. Do not turn your thumbs up and down on this motion, just keep your palms facing down.
3), IMO, one of the best rear delt exercises is to do seated rows on a row machine, but use a tricep rope. When you pull the rope toward your chest, pull your hands apart and try to pull the rope up toward your chest a bit instead of pulling it straight into your trunk. Use a lower weight to isolate the rear delts. You'll be sore as shit the next day.
FOR ROTATOR CUFFS:
There are 4 muscles that make up the RC: infraspinatus, subscapularis, supraspinatus, and the teres minor. Together, these tiny muscles stabilize the shoulder and allow for the shoulders wide range of motion. You only have to damage one for your shoulder to go to hell. I had an 80% tear of the supraspinatus and had a hell of a time functioning. The infraspinatus and the teres minor are the hardest to isolate adn they cause the most problems. These muscles control external rotation (i.e.: hold your arm bent at a 90 degree angle with your elbow against your body and your hand in front of your body...now rotate your forearm away from your body....that involves the Infraspinatus and the teres minor.) The subscapularis controls motions that involve the opposite: it works to pull your arm in towards your body. The supraspinatus functions to allow you to raise your arm over your head and move your arm in various directions. This muscle is critical in that is bears much of the load for your shouler joint when you bench press, military press, etc.
TERES MINOR/INFRASPINATUS EXERCISES:
1) External rotations: I do these 2 different ways: a) use a rubber band to perfrom the external rotations, making sure you keep your elbow against your body. It helps to roll a bath towel up into a ball and place it under your elbow for support. b) I sit sideways on a preacher curl station and place my elbow on top of the pad. I then raise and lower my arm using a 5-10 Lb. DB. I typically do sets of 15 reps. You don't want to completely exhaust these muscles, so don't go to failure.
2) Cuban presses: these are difficult to explain, so go here:
Cuban Press
They illustrate them with a DB, but you can use an EZ curl bar. Just do an upright row, externally rotate the bar over your head, then press it straight up. Follow the same motion down.
SUBSCAPULARIS EXERCISES:
1) use the rubber bands again, except this time rotate them internally.
SUPRASPINATUS EXERCISES:
1) L-Lateral raises: Bend your arms at a 90 degree angle, do a side lateral raise to parallel with the ground. At the top of this motion, you can do an external rotation to hit the Teres minor and infraspinatus.
2) Regular lateral raises
3) The BEST exercise for this muscle goes like this: lay on your side on a flat bench. Holding a DB with your thumbs pointed DOWN, do a lateral raise, but only go until your arm is at a 45 degree angle. Hold for 2 seconds, adn come down slowly.
Some of these exercises can be found at: http://www.t-nation.com/findArticle.do?article=280rotator2
Give some of these a shot and see what happens. It doesn't take much to effectively work the RC, so go light. You don't have to do 10 sets either. I usually just do 6-8 sets at the end of a workout 2 x per week. It's done wonders for me.
