#3: Straightening Your Arm on Rear Delt Exercises
The same blunder involving elbow extension frequently makes its way over to rear delt exercises, most commonly bent-over lateral raises with dumbbells or cables. When you extend at the elbow, you turn a perfectly good rear-delt exercise into one for triceps. Again the key is to lock your arm in a slightly bent position for the duration of the set. If you’re not getting the hang of it, practice doing the reverse fly on the pec-deck machine, which requires you to maintain a slight bed for the entire exercise.
#4 Hands Too Close on Upright Rows
To target middle delts, your upper arms should travel out to your sides during upright rows. That’s not what happens, however, when you use a close grip. Your elbows are drawn forward as your shoulders are internally rotated. That movement isn’t kind to your shoulder joints. A much wider grip (hands about shoulder width apart) allows your elbows to kick out high and wide, perfect for targeting your middle delts. (The front delts get some work, too.) Even if you’re looking to add variety to your routine, skip the close-grip version.
#5: Neglecting Your Rotator-Cuff Muscles
Sure, you want big shoulders, and that means choosing exercises that target the front, middle and rear delts. However, a smaller group of four rotator cuff muscles also work in tandem to help stabilize your shoulder joint (and that includes during presses for the chest). As your delts grow stronger over time, and if you’re not also training your rotator-cuff muscles, a strength imbalance arises that makes the rotators much more susceptible to injury and chronic pain.
Doing specific rotator cuff work with extremely light dumbbells, cables and bands may not look impressive, but it’s a necessity for long-term pain-free training.