If I surveyed 100 meatheads and asked them, “what is the best exercise for the rear delts?” 99 of them would answer “reverse flyes.”
The seated reverse flye is the most common exercise used to target the rear delts. It makes sense because the reverse flye motion does a good job of isolating the rear delts—the exercise isn’t optimal, though.
The seated dumbbell (DB) reverse flye suffers from a couple of significant flaws and in training, the exercise does not match the muscle’s strength curve. The strength curve of the delts in isolation exercises is bell-shaped. This means that you are strongest in the mid-range and weaker at the start and end ranges.
The resistance profile of the DB reverse flye means the load is heaviest at the top and lightest at the bottom because the torque required to lift the load is greater the further from the body the arm moves. At the bottom of the lift the arm is by your side. At the top it is way out to your side. This long lever arm means the weight feels much heavier in this position.
The DB reverse flye does not match up with the muscle’s profile and, therefore, you are not fully challenging it throughout the lift. Instead, it is very easy at the bottom and an absolute killer at the top. The muscle is only being challenged through a small part of the range and the weight you can use is limited by what you can handle at the top.
Fix Your Flyes
Fixing this issue is actually very simple. Do the side lying DB reverse flye. By manipulating your body position, you can create an exercise that matches the rear delt’s strength profile and provides an appropriate challenge throughout the entire range.
By lying side on to the bench when you perform the lift you can create a resistance profile where the lift matches the muscle’s capacity closely. Because of your position, the lever arm is very small to begin with and increases as you move through the mid-range before dropping off at the end.
This is ideal and means the rear delts are stimulated through every inch of every rep. More stimulus equals more gains.