Justin Martin on Instagram: "This is my current workout to target my underdeveloped rear delts. I perform each exercise for 4 sets reaching complete failure in the 8-10 rep range. It does not take much work to stimulate the rear delt but this muscle is so often overlooked and underdeveloped. And yes, I meant reverse cable flys!!😁 What is your favorite rear delt exercise?? #workout #fitness #shoulders #delts"