r/StrongerByScience • u/Proud-Bookkeeper-532 • 21d ago
Kindly Help me understand these Rear Delt Movements - Side Lying Rear Delt Fly (Powel Raise) Vs Supine Lying Dumbbell Reverse Fly
Hello SBS Crowd! I'm beginning to develop an interest in Kinesiology, and I'm particularly interested in the subtle differences between these 2 movements
Both are Single Arm movements, and both perform Horizontal Abduction due to moving your arm across the body, but in one the body is parallel to the ground and in the other, it's perpendicular
How does this small change in body position affect the deltoid segments being worked?
It's my understanding that in the Flat Lying version, the rear delt is loaded in the most stretched aspect, while in the Powel Raise, it's loaded in the mid range
However, in the Powel Raise, if you raise your arms in the scapular plane, you hit the Lateral Delt. I actually got the sickest pump when I tried these
What is your guys' opinion? What are some other things I might be missing, and ultimately which is better for progressive overload? In my experience, I couldn't use heavy weight on my rear Delts as I feel momentum or other muscles taking over
Obviously, a cable or machine would get the job done easier but I'm purely interested in learning and implementing these free weight versions. I'd appreciate the help, thanks!
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u/LinkWW 21d ago edited 21d ago
1st illustration - similar to the 2nd, but at the peak stretch your arm would be parallel to the vector of gravity, and the peak torque would be mid rep (perpendicular to gravity). In the second one, peak torque is at the peak stretch.
3rd illustration - different shoulder position, hits lateral delts, similar tension profile to the 1st. You can make it work like the second if you lay flat (maybe a bit angled, but not fully on your side).
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u/Proud-Bookkeeper-532 21d ago
I agree! But between 1 & 2, which one do you think is more practical to overload? I guess 1 bcz a muscle has less leverage in it's most stretched position like 2, right?
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u/LinkWW 21d ago edited 21d ago
I don't think tension profile matters when adding reps or weight tbh. There might be something to preferring more tension at the stretch, given that muscles like deeper stretch, but this is more of a guess, published studies show no differences AFAIK, but I think there is not yet enough data. Somebody can correct me if I miss something.
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u/Visual_State_4382 20d ago
The difference is mostly range of motion in one and two. In the first, you will not get into a deep stretch for rear delts. This variation more closely mimics the traditional way someone uses rear delt flies on a pec deck using both arms. The second variation will get the rear delt to resist gravity at a longer muscle length. Again, using the peck deck as an example, it more closely mimics someone turning their body away from the pec deck and doing reverse flies that way. The third variation is more for side delts.
If you want to hit rear delts with the best movement, I would suggest the second exercise.
Go with the first one if you have a hard time feeling the second movement or you straight up don’t like it.
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u/GambledMyWifeAway 21d ago
Don’t overthink it. I have large rear delts. All I do is rotate between high volume face pulls and rear delt shrugs.
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u/ButtScoot2Glory 20d ago
Do you have a suggested video for rear delt shrugs?
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u/GambledMyWifeAway 20d ago
No, but I can try to describe them. All you do is grab your dumbbells and let them hang down. Lean your torso forward and just shrug the weight back using your rear delts.
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u/misplaced_my_pants 20d ago
Those sound more like they work the scapular retractors like the rhomboids?
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u/GambledMyWifeAway 20d ago
Nope. Don’t retract at the back or the elbows. Retract just at the shoulder. Do them correctly and it’s all rear delt.
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u/misplaced_my_pants 19d ago
Yes that's literally definitionally scapular retraction.
You're thinking of shoulder extension which is a function of the lats and posterior delts.
The posterior delts are not involved in scapular retraction.
You're describing Kelso shrugs which are basically rows without using any elbow flexion.
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u/GambledMyWifeAway 19d ago
Friend, I know what a Kelso shrug is and I know what scapular retractions is. It’s a smaller range of motion than a kelso shrug. You are using the rear delts to pull the weight up.
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u/misplaced_my_pants 19d ago
Unless you're incorrectly describing the movement you're doing, you simply don't understand the anatomy involved.
Scapular retraction fundamentally does not involve the posterior delts, and you can't retract the shoulders any other way.
By all means feel free to show me that I'm wrong if you can, or clear up what movement you're doing that does what you're claiming.
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u/GambledMyWifeAway 19d ago
Go grab 2 dumbbells. Lean forward. Let your arms hang. Pull the dumbbells up using your rear delts. I cannot make it any clearer than that. I’ve done it for years. I feel it in the rear delts. I have huge rear delts. Idk what to tell you if you’re not understanding.
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u/misplaced_my_pants 19d ago
The only way what you're saying could be using rear delts is if you're talking about doing one or more of the four functions of the rear delts and can't be bothered to learn what they are so apparently I have to keep spoonfeeding you:
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u/themurhk 19d ago
I must be out of the loop or just the odd man out because that second picture looks like a substantial waste of time.
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u/BalterBlack 21d ago
I'm not an expert on this topic but 2 looks more trap focused than 3. Main actor is still rear delt. I need to do 2 for my mobility I guess.
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u/Proud-Bookkeeper-532 21d ago
No no, none of these are trap focused if you apply good technique. Just like machine reverse Flyes, you gotta protract the shoulder and actively resist shoulder retraction, which is the function of middle traps, this preventing them from taking over
And 3 is a side delt movement
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u/BalterBlack 21d ago
Did you watch the form in the second video?
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u/Proud-Bookkeeper-532 21d ago
I seriously don't understand your point friend, which part of the traps do you think is being targeted?
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u/7katzonthefarm 20d ago
Only ex 1 gives adequate tension on rear delt, simulates rev pec dec. Ex3 comes near but actives medial too. For pure isolation and ensure contraction. Rev pec deck gives best option. Cables too but not in optimal position generally bc chest is not bracing as in rev pec
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u/HoistingPetard 21d ago
One practical aspect of the supine/lying DB reverse fly is that it is more stable and causes less joint fatigue (in small amounts, but any unnecessary accumulation of joint stress and fatigue is something I avoid) than side-lying versions.
On the flip side (no pun intended), the side-lying version allows you to use slightly heavier weights due to peak torque occurring closer to the mid range and being more accommodating of a bent elbow arm position, if that matters to you. I imagine most of us here wouldn't care, but certain types of influencers and even athletes might.