How to Isolate Rear Delts…
What is the least understood and well trained muscle in the body for most gym goers?
Good guess – the title totally didn’t give it away – it’s rear delts.
See, it’s one of those muscles that isn’t especially sexy, you don’t lift much weight and you can’t see them yourself. You’re told you should train the muscles that support your back and shoulders, they’re the foundation and all that. Problem is, it’s difficult to isolate them properly. Especially when very few people actually understand their function. Or perhaps more accurately have ever actually considered their function, instead of just doing rear delt flyes and face pulls, because ‘that’s what you’re supposed to do, bro’.
Rear delt flyes and face pulls are both good exercises by the way, not dissing them as movements. Problem is most people just move weight from point A to point B instead of thinking about what they’re doing and executing the movement with the muscles they’re aiming at.
I’ll tell you exactly how to perform these exercises to isolate the rear delts, for growth and shoulder balance. First a quick and dirty anatomy lesson.
Rear delt’s function
The rear (posterior) deltoids functions are shoulder extension, external rotation, transverse extension & transverse abduction. In English that is:
- shoulder extension – moving the arm behind the body
- external rotation – rotating the arm from thumb facing in to thumb facing out when arms hang vertical
- transverse extension – moving the arm sideways away from the body with elbow facing out
- transverse abduction – moving the arm away from the body with elbow facing down
In exercise terms, the rear delts main job is to pull the arm behind the body in exercises such as pull ups, rows and of course rear delt flyes, face pulls and all of the other targeted rear delt exercises.
What they do not do, is move the shoulder blades.
Most people do rear delt exercises wrong…
…because they move the shoulder blades in to retraction.
This might sound contrarian because you’ve always been told by the guru’s that you should retract your shoulders at any opportunity, because…posture. While that isn’t usually a bad idea, because most people’s posture does suck, it’s going to kill rear delt activation. Here’s why:
The muscles that retract the scapulae (shoulder blades); namely the mid traps and rhomboids are doing most of the work. The rear delts are active – the arm is moving along with the shoulder blades. However the movement is driven from the shoulder blades and is not isolating the rear delts in the way that people hope. Frankly, you probably get a better rear delt workout doing pull ups and rows, because you still initiate from the scapula (and elbow), but you’re using significantly more weight.
How to isolate rear delts
To actually isolate the rear delts the shoulder blades shouldn’t move. Fully protract (push forward) the shoulder blades and keep them there throughout rear delt isolation exercises to properly isolate rear delts and take the scapula retractors out of the movement. Even fully retracting them is inferior because they have to maintain that, meaning they are under isometric tension, and often the weight will overpower this isometric and move them anyway, so they still end up moving when you try to keep them fully retracted.
Keep them fully protracted to keep the muscles ‘turned off’ and focus only on the rear delts.
This goes only for isolation exercises. I do not advise scapula protraction in compound lifts. That’s asking to impinge your shoulder or at least train you in to sucky posture. The purpose of this technique is only for rear delt isolation.
How to train rear delts
What you’ll find when you do this, is that your weights go way down. Suddenly you’re not as strong as you thought you were. Use light weight and high reps for rear delts. They’re more slow twitch fibres than fast, and they get hit with heavy weights and lower reps on pull ups and rows anyway.
Think 20-50 reps, controlled tempo and what will feel like a short range of motion. When you take your shoulder blades out of it, your rear delts will only move your arm, roughly from straight in front of you, 75 degrees to just before straight out sideways.
The best rear delt exercises in my opinion are band pull aparts (protracted shoulders), rear delt flyes on the pec deck (protracted shoulders) and bent over/face down flyes with dumbbells (shoulders protracted). Choose one of those as they’re all very similar and couple with face pulls (neutral shoulders). The face pulls will also hit the external rotation component of the rear delts.
Rear delt demonstrations
In the video below you will see the difference between isolated rear delts with no scapula movement, and the mistake that many people make, moving the shoulder blades. Notice how much shorter the range of motion is, and how obviously weaker it is, by the speed of movement..
Using this rear delt knowledge in the gym
Go ahead and give it a crack next time you’re training rear delts. Be sure to take it light and slow, to focus on the movement and building mind-muscle connection. You should be able to get a good burn within a set of two and really feel the difference compared to throwing weight around from point A to point B.
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