This is a rather weird-looking exercise, but it's a very effective way to build the whole deltoid with an emphasis on the lateral portion.
Basically, the movement is like performing a one-arm lateral raise while the other arm is brought up with the elbow bent at a 90 degree angle. The bent arm doesn't do much work because of the advantageous lever, but it allows you to keep some tension on the shoulder muscle during the whole exercise. Constant tension equals more growth!
For novice lifters, the focus on staying extremely lean ruins their progress. Here’s what those little weak guys need to accept if they want to become big strong guys.
Screw the rotator cuff! That's right, screw it. When it comes to fixing shoulder pain, the the rotator cuff is over-hyped and gets way too much attention.