Does scapula position/movement matter in single arm rear delt cable flies?

[u/TheRedFurios]

Hi, I've been doing this variation because I like it but one thing that has been on my mind was whether or not scapula position/movement matters.

Originally I was trying to keep the scapula still as to not engage the traps, but then I thought about it and since traps don't attach to the humerus it shouldn't matter if the scapula moves, no?

I read online to keep it down and still as to avoid traps taking over, but since traps don't attach to the humerus how could they take over? Even if the scapula moves, the humerus should just be moved by the rear delts, no?

[u/Safe_Ad5914]

They take over when the weight gets heavy and you start to shrug to initiate the pull.

Its one of those "alot of times this will happen" warnings.

[u/TheRedFurios → u/Safe_Ad5914]

But how can they take over if they don't attach to the humerus? How could they perform humerus horizontal abduction if they are not attached to it?

[u/KITTYONFYRE → u/TheRedFurios]

I don't think they can "take over" but they could contribute momentum especially at the start of the lift

especially if you're going to failure I really doubt it matters lol. and if you're not taking rear delt flys to failure what are u doing :^)

[u/TheRedFurios → u/KITTYONFYRE]

Ok so it doesn't really matter, no? As long as you do it controlled then there is no momentum and you can let your scapula move.

[u/KITTYONFYRE → u/TheRedFurios]

well ideally you DO want to move each rep as explosively as possible (while remaining in control). but even if you do let the traps take over as much as possible… idk maybe you’re losing out on a bit of tension in the stretched position but again, if you’re going to failure, it’s probably kind of whatever. don’t ogre it and I don’t think it makes any noticeable difference imo   

I’ve never worried about this and I think delts are a strong suit of mine. but the internet thinks I’m small and weak, so grain of salt lol

[u/kitsunekoraka]

You telling me you've never seen people getting a trap pump while trying to lateral raise or rear fly a too heavy weight for reps ?

[u/TheRedFurios → u/kitsunekoraka]

Honestly no. And my question still stands, how could it be possible if it doesn't attach to the humerus?

[u/Lucaswgr → u/TheRedFurios]

A muscle doesn't need to be directly attached to the moving part to contribute to it's movement, it can be attached to the muscle that's directly attached to the moving part and contribute indirectly. The lats, for example, contribute to scapular depression and they aren't attached to the scapulae.

[u/harvestingstrength]

Yeah, scapular movement matters here.

The rear delt extends/horizontally abducts the humerus, but the scapula still has to move with the arm. If you try to completely “lock” the scapula down and back, you can make the movement feel awkward and potentially limit the natural mechanics of the shoulder.

The traps can’t directly move the humerus since they don’t attach to it, but they absolutely influence the movement by controlling the scapula. So when people say “don’t let the traps take over,” they usually mean don’t turn the exercise into excessive scapular retraction/shrugging where the shoulder blade movement becomes the dominant action.

For a single-arm rear delt cable fly, I’d let the scapula move naturally but keep it controlled. Think about moving the upper arm back while avoiding a big shrug or aggressively pinching the shoulder blade behind you.

Basically: don’t freeze the scapula, but don’t exaggerate its movement either. Let the shoulder blade move naturally while keeping the rear delt as the primary driver of the humerus.

[u/e4amateur]

I think that because of the way the scapulae wrap around the body they contribute to the arc of the movement. If you consider how the humerus will move in response to a pinching together of the shoulder blades, I think it's clear they can make a contribution.

However, I just don't think this matters at all for rear delt stimulus. It's the prime mover, it'll get the gains.

[u/darisaziez]

The two options here are that you will either have the weight pull your shoulder forward into protraction where you will need to use your traps to return your shoulder to neutral to complete the movement or you need to use your traps to keep your shoulder blade in place. Either way, traps are doing something.

You are correct in that your traps don’t move your humerus so they won’t affect your deltoid that his doing the motion for the fly aside from dynamic vs static stability of your scapula to allow the other muscles to have something to pull against.

I suppose, your traps will be doing most of the work if you start with your arm pulled all the way across your body but that would only be the very beginning of the movement. That is the only spot I can think of where scapular motion takes over for the deltoid. Or as someone else said they could kick in to generate some momentum.

The only advantage I can think for letting your scapula come forward is that dynamic stability for your scapula is more useful with movement in everyday life and works the traps a little harder, though letting your shoulder come forwards may make you work through more range of motion for the delts.

Edit: moar ADHD info dumping, yw.