Okay, first the big statement in this article, and I want you to listen to this part very carefully: You have been doing your front and rear raises all wrong. There. I want you to read that over a few times and let it sink in. There's nothing to be ashamed of, it's true for most. Very few trainers do their front raises right, and to this day I have yet to see anyone doing rear raises correctly. But why? The reason is: Nearly all trainers do all types of raises with their side delts. Think about it. When doing front raises, how do you hold the dumbbell? Palm down most likely.
And during your bent over raises? Palms down again. Now hold your arm out with your palm down. Which delt head is facing up? It's not your front. The front will be contracted, yes, but the side delt will be taking the brunt of the force.
So why is THAT? It's all because of the position of the shoulder. Why do military presses work the front delt? Because the front head is the one directly along the line of stress. Okay, that was a complex sentence. Let's simplify things: in any dumbbell movement, the direction of the stress is down towards the floor. Naturally, we want the muscle facing the ceiling, then. So, logically, for front raises we want the front delt facing up, for side raises the side, and for rear raises the rear.
Back to arm position now, in military presses the front delt head is facing up. Now extend your arms outward and make sure the front delt is still facing up. What direction is your hand in? Hammer grip. Now do the motion of a front raise with a hammer grip. Which head is facing up? That's right, the front.
So now we have a way to think of things. If you haven't been paying attention up to now, that's okay. Here's the take-home part: Think of your hand like your shoulder. Make a fist. This is now your shoulder, for all intents and purposes. The thumb side is your front delt, the back of your hand is the side, the pinky side is your rear delt. Whichever side is facing the ceiling is the one that's getting used.
So for bent-over raises, you'd want to hold the dumbbells so your palms are facing the wall behind you, not facing each other. For front raises, a hammer grip, and for side raises, the conventional palms-facing the floor. Without using this targeted approach to delt training, it's nearly impossible to get evenly developed shoulders.