Despite the fact that lots of guys include rear delt work, they usually initiate the exercises with the traps and rhomboids, so the poor little posterior delts get very little attention.
Going too heavy can be one of the culprits here, but the other problem is that they don't begin the movement with the scapula properly set. Here's how to do that with a great rear delt exercise – seated cable rear laterals:
Seated Cable Rear Laterals (Posterior Delts)
Begin with the cables set up in line with the rear delts, and with the scaps in protraction. Then you should feel the posterior delts catch fire during the set. If that isn't happening, then you're still most likely initiating with the traps and upper back or calling them into play too much during the set.
It's also difficult to establish a mind/muscle connection with the posterior delts, which is another reason why this muscle group often lags behind. The bigger and stronger areas of the upper back are built for big work and love to take over on pulling movements. The posterior delts still get some love, but not enough to grow to their potential.
This is why movement execution is paramount – even more important than progression. Feel the rear delts. Kill the rear delts. See the growth happen.
Intensity Method: Drop Sets
Once you've mastered the form, bludgeon your rear delts into growth with this intensity method:
- Choose a weight that allows you to hit 10 solid reps in good form, but most likely not 11. Do a set there.
- Without rest, reduce the weight and shoot for 10 more reps.
- Immediately reduce the weight again and shoot for another 10 reps.
- Rest for a couple of minutes, then repeat that drop set two more times for a total of 90 reps.
If you can't feel your rear delts getting blasted, then you simply aren't in possession of posterior deltoids.