# Dumbbell Lying One Arm Deltoid Rear - Canonical: https://fitwill.app/exercise/11354/dumbbell-lying-one-arm-deltoid-rear/ - Media ID: 11354 - Primary muscle: Shoulders - Body part: Shoulders - Equipment: Dumbbell - Video: https://fitwill.app/videos/11354/dumbbell-lying-one-arm-deltoid-rear.mp4 ## Description The Dumbbell Lying One Arm Deltoid Rear is a side-lying rear delt raise performed on a flat bench. You lie on your side with a dumbbell in your top hand, then sweep the arm up in a wide arc until it points toward the ceiling before lowering it back down with control. Because your body stabilizes you against the bench, the working shoulder gets isolated without needing to fight gravity or balance a standing position. This movement primarily targets the rear deltoid, the muscle at the back of the shoulder, along with the rhomboids and mid-traps that pull the shoulder blade in toward the spine. These are the muscles most people undertrain, since pressing and front-raising work dominate most routines. Strengthening them supports better shoulder posture and balances out all the pushing work in a typical program. The side-lying setup matters more than it looks. Lying on the bench locks your torso in place, which removes the cheating options you have when standing: no torso swing, no body english, no driving with the legs. Your bottom arm reaches down to brace against the floor or bench frame, and your legs stay stacked and still. That fixed position forces the shoulder itself to do the lifting. To perform it well, focus on sweeping the arm in a smooth arc rather than jerking it up. The weight should travel in a wide semicircle until your arm is roughly vertical, and you should feel the squeeze between your shoulder blade and spine at the top. Pause there briefly, then lower the dumbbell slowly, resisting gravity all the way down instead of letting it drop. This exercise suits lifters who want targeted rear delt work without heavy loads, people dealing with shoulder imbalances from lots of bench pressing, and anyone who finds bent-over raises hard on the lower back. Because each arm works alone, it also exposes and helps correct side-to-side differences. Keep the weight modest. This is a small muscle working through a long lever, so strict, slow reps with a light dumbbell beat heavy, jerky ones every time. Stop each set when the arc becomes hard to control, not when the muscle simply burns. ## Instructions 1. Set a flat bench to its level position and lie on your left side along it, with your torso near the top edge and your legs stacked on the bench or resting on the floor. 2. Hold a dumbbell in your right (top) hand with a neutral grip, palm facing the floor, and let the arm hang straight down toward the floor so it is roughly perpendicular to your torso. 3. Extend your bottom (left) arm down to brace against the floor or grip the bench leg, and keep your head in line with your spine rather than craning it up. 4. Brace your core lightly and squeeze your legs together so your torso cannot roll backward during the set. 5. Raise the dumbbell in a wide arc, leading with the elbow staying slightly bent, until your arm is vertical and points toward the ceiling. 6. Pause for a beat at the top and feel the contraction across the back of your shoulder and between your shoulder blades. 7. Lower the dumbbell along the same arc over two to three seconds until your arm hangs fully down again without the weight touching the floor. 8. Exhale as you raise the arm and inhale as you lower it, keeping your breathing steady throughout. 9. Complete all reps on one side, then roll over and perform the same number on the other arm before finishing the set. ## Tips & Tricks - The most common mistake is rolling the torso backward to help the dumbbell up, which turns a shoulder exercise into a twisting motion; keep your chest stacked over the bench and let your brace arm anchor you. - Use a lighter weight than you would for a standing lateral raise, since the long arm lever makes the same dumbbell feel significantly heavier from this position. - Keep the elbow bend fixed at roughly 10-20 degrees throughout; straightening and bending the arm mid-rep turns the movement into a triceps exercise. - If your arm hangs too close to the bench edge, shift your torso so the dumbbell clears the bench on the way down, or the weight will clank or pull you off balance. - Do not crane your neck to watch the dumbbell; resting your head slightly on the bench or keeping your gaze straight down protects your neck and helps you feel the shoulder working. - Aim for a smooth arc, not a straight pull out to the side; lifting the weight straight up reduces the rear delt's range and shifts work to the traps. - Lowering fast is the easiest rep to waste; the two-to-three second descent is where most of the rear delt and rhomboid work actually happens. - If you feel a pinch at the very top, stop slightly short of vertical and work within the arc you can move smoothly rather than forcing full height. ## Frequently Asked Questions ### Which muscles does the Dumbbell Lying One Arm Deltoid Rear work? The rear deltoid at the back of the shoulder is the primary mover, with the rhomboids and middle trapezius assisting as the shoulder blade pulls in. Small stabilizers around the rotator cuff also contribute to controlling the arc. ### Why lie on your side instead of doing bent-over rear delt raises? Lying on the bench locks your torso in place, so you cannot swing your body or recruit momentum the way you can when bent over. It also removes strain on the lower back, which some people feel during bent-over positions. ### How heavy should the dumbbell be for this exercise? Start noticeably lighter than you would use for a standing lateral raise, often 5-15 pounds depending on experience. If you have to roll your torso or jerk the weight to finish a rep, the dumbbell is too heavy. ### How high should I raise the dumbbell at the top of the movement? Raise it until your arm is roughly vertical and points toward the ceiling, which is roughly a 90-100 degree arc from the hanging start. If the top of the range causes pinching, stop a few degrees short and keep the motion smooth. ### Should I do both arms in the same set or alternate? Finish all reps on one side, then roll over and work the other arm. Doing one side completely first makes it easy to match the exact rep count and keeps your setup on the bench simple. ### Can beginners do the Dumbbell Lying One Arm Deltoid Rear? Yes, and it is actually a beginner-friendly way to train the rear delts because the bench supports the body and removes balance demands. Begin with a very light dumbbell and focus on a slow, controlled arc before adding weight. ### What can I use if I don't have a flat bench? You can lie on your side on the floor or on a firm mat and perform the same arcing raise, though the floor will stop the dumbbell at the bottom of the range. A stability ball is not recommended here because the torso needs a stable surface. ### How many sets and reps should I do? Two to four sets of 10-15 controlled reps per arm works well, since the rear delt responds to strict reps with moderate loads. Add weight only when you can complete all reps without rolling your torso or dropping the descent speed. ### Is it normal to feel this more in the shoulder blade than the shoulder? Feeling some work between the shoulder blades is expected because the rhomboids and mid-traps assist the rear delt. If the shoulder blade does all the work and the back of the shoulder feels nothing, reduce the weight and focus on leading with the arm rather than squeezing the blade first.