You’ve probably seen the guy at the gym standing in the cable crossover machine, looking like he’s trying to scratch an itch on his lower back while holding a handle. It looks awkward. It feels a bit weird the first time you try it. But honestly, behind the back lateral raises might be the only reason some people actually develop that "capped" shoulder look.
Most people just spam dumbbell side raises. They stand there, swinging weights like they’re trying to fly away, and wonder why their medial deltoids aren't growing. The problem is physics. With a dumbbell, there is zero tension at the bottom of the movement. Your arm is just hanging there. Gravity is pulling the weight straight down into the floor, not against your muscle.
Switching to the cable version changes the profile. By placing the cable behind your back, you’re forcing the medial delt into a stretched position it rarely sees. It’s a game-changer.
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The science of the stretch-mediated hypertrophy
We used to think muscles only grew from being crushed under heavy loads or "feeling the burn." We were wrong. Recent research, like the studies often cited by Dr. Mike Israetel of Renaissance Periodization, suggests that "stretch-mediated hypertrophy" is a massive driver of muscle growth. Basically, if you can challenge a muscle while it is in its longest, most stretched state, you trigger more growth signaling.
Standard lateral raises are hardest at the top. That's when your arm is parallel to the floor. Behind the back lateral raises are different because the cable is pulling your arm across your body and slightly behind your hips.
This puts the side delt under intense tension right at the start.
If you look at the anatomy of the shoulder, the middle deltoid fibers originate on the acromion and insert into the humerus. When your arm is behind your back, those fibers are elongated. If you start the pull from there, you’re hitting those fibers when they are most vulnerable and most likely to grow. It’s also harder to cheat. You can’t really use your traps as much when the cable is routed behind your glutes.
Setting it up without looking like a total amateur
Don't just grab the cable and pull. You'll probably hurt your rotator cuff or just feel a whole lot of nothing.
First, set the pulley height. Most people set it at the very bottom, but that creates a really sharp angle that can be tough on the joint. Try setting it around mid-shin or even knee height. This keeps the tension consistent throughout the entire arc.
You want to stand slightly in front of the cable machine. Not miles away, just a few inches. Reach behind your back and grab the single D-handle with the hand furthest from the machine.
Now, the lean.
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A slight lean away from the machine—maybe 10 to 15 degrees—increases the range of motion even further. It keeps the cable from rubbing against your butt and lets the delt work in a larger window. Keep your chest up. Don't let your shoulder roll forward. If your shoulder rounds, you’re just hitting your front delt and risking an impingement.
Why cables beat dumbbells every single time for side delts
Dumbbells are great for rows and presses. For lateral raises? They’re kinda trash.
The resistance curve of a dumbbell lateral raise is a bell curve that peaks at the very top and drops to zero at the bottom. The cable provides constant tension. Behind the back lateral raises ensure that from the millisecond you start moving your hand, the muscle is fighting.
There's also the issue of the supraspinatus. That's a tiny rotator cuff muscle that does the first 15 degrees of a lateral raise. When you do dumbbells, the supraspinatus does most of the heavy lifting to get the weight moving. By the time the side delt takes over, you’re already halfway through the rep. Cables, especially behind the back, force the side delt to engage much earlier.
Common mistakes that kill your gains
Stop using too much weight. Seriously.
The side delt is a relatively small muscle. If you’re using 40-pound cables for behind the back raises, you’re likely using your hips, your traps, and your ego. You’ll know you’re doing it wrong if you feel a "tug" in your neck. That’s your levator scapulae and upper traps screaming for help because your shoulder can't handle the load.
- The "Bicep Curl" Mistake: People often bend their elbow too much. If your elbow is bent at 90 degrees, you've shortened the lever arm and made the exercise easier, but you're also likely involving the biceps. Keep a very slight, "soft" bend in the elbow.
- Wrist Flicking: Don't lead with your knuckles. Lead with your elbow. Think about pushing the weight out toward the walls, not up toward the ceiling.
- Speeding: If you’re snapping the weight up and letting it crash down, you’re wasting half the rep. The eccentric (the way down) is where a lot of the muscle damage—the good kind—happens.
Integrating this into your split
You don't need to do 10 sets of these. Because the tension is so high, 2 to 3 sets of 12-15 reps is usually plenty.
Try doing these at the end of your shoulder workout. Your delts will already be pumped and full of blood, and this will finish them off. Or, if your side delts are a major weak point, do them first. Start with your weakest arm. Most people have a dominant side that takes over, so start with the left (if you're right-handed), match the reps with your right, and move on.
Real-world results and expert takes
Bodybuilders like John Meadows (the Mountain Dog) and coaches like Joe Bennett (The Hypertrophy Coach) have long championed cable variations for lateral raises. They emphasize the "y-plane" movement. This means moving your arm slightly forward and out, rather than strictly to the side. Behind the back lateral raises naturally encourage this path because of where the cable originates.
It's also safer for people with "junky" shoulders. Moving the arm behind the torso can sometimes clear the subacromial space better than a standard front-of-body cable raise, which often causes people to shrug and pinch the tendons in their shoulder.
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Actionable steps for your next shoulder day
Don't just read this and go back to your 20-pound dumbbells. Actually change the way you train.
Next time you hit the gym, head straight for the cable station. Set the pulley to knee height. Position yourself a half-step in front of the line of the cable. Reach behind your glutes and grab the handle. Lean slightly away.
Execute your reps slowly. Focus on the stretch at the bottom. If you can’t pause for a split second at the bottom without the weight stack hitting, you’re standing too close.
Next steps:
- Set the pulley height: Start at knee level to find the smoothest path.
- Master the lean: Use the non-working arm to hold onto the cable upright for stability.
- Tempo check: Use a 2-second concentric (up) and a 3-second eccentric (down).
- Volume: Aim for 3 sets of 15 reps, focusing purely on the mind-muscle connection rather than the weight on the stack.
You will likely find that you have to use a much lower weight than you expect. That’s normal. It’s the sign that you’re finally actually hitting the muscle instead of just moving a weight.