Why are they more effective than standard lateral raises?
Although the motion is exactly the same, the difference is found in the way the medial delts must produce force in the lifts. In the standard lateral, the medial delts are working hardest at the top of the lift, when the arm is fully extended away from the body and parallel to the ground. As such the muscles only need to exert their peak contraction at the top of the lift. In a lying lateral raise, the arm begins slightly below parallel to the floor. The force required to lift the weight is maximal when the arms are parallel to the floor, i.e. just after the lift has begun. As a result, the medial delts are working hardest at the start of the lift. Many people find that by training their medial delts in this way, where they are working hardest near the bottom of the movement than at the top, they work the side shoulders much more thoroughly, and thus experience more growth. Try it for yourself – you’ll feel the difference in one workout. You’ll be able to lift significantly less weight
