I'm Jeremy Shore for LIVESTRONG.COM, and this is how to work the rear deltoids. The rear deltoid muscles contribute to the size and shape of the shoulders. They also serve to balance; they overwork anterior deltoids and the pectorals. There are two great exercises you can use to strengthen and build your deltoids. The first is an endurance series called an IYTW. You're going to come to a prong position on the mat, face down, chin's tucked in. The hands are extended straight up overhead, so your body forms a straight line, we'd resemble and I. From here, you're just going to lift the thumbs towards the ceiling, up and down, keep the glutes tight. From there, we'll do ten repetitions, then we're going to move into a Y with the arms, keeping the arms straight, thumbs up still towards the ceiling; eyes down, chin in, glutes tight, we'll go up and down for ten repetitions. So, next, we'll move into a T, thumbs will still move toward the ceiling, chin tucked in, retracting the shoulder blades, for ten repetitions. Then we'll finish with the W or a Cobra. Palms down, chin tucked, you want to draw the backs of the hands towards one another, squeezing the shoulder blades together and allowing them to travel down the back and return to that T position. Keep the glutes tight, repeat for ten repetitions. Then, to develop strength in the rear deltoid muscles, we can do a dumbbell row on a bench. Lie face down on a bench that's set to a slight incline. Dumbbells are position, be positioned directly under your shoulders, chin's pulled in, glutes are tight. From here, we're going to row and draw the elbows towards the ceiling and then control the weights back down. Retract the scapula at the top and slow the weight as you lower it back towards the ground. I'm Jeremy Shore for LIVESTRONG.COM and this has been how to work the rear deltoids.