Correcting rounded shoulders by adjusting sleeping position, arms going numb

Question

I suffer from rounded shoulders and a slightly forward neck due to bad sitting posture and anterior pelvic tilt which has shortened my hip flexors causing my upper back to compensate by hyperkyphosis. I'm trying to correct all of this now and one of the things I want to do is change my sleeping position. Because our muscles tend to adapt to the positions we keep them in, and I often sleep on my sides with my shoulders somewhat rounded, I have decided to start sleeping on my back.

Moreover, rather than keeping my arms by my sides, I wanted to try to keep my arms in the same position they would be in when performing wall slides, which is one of the exercises I learned is good for correcting rounded shoulders (here and here). In the wall slide, the heels, butt, upper back, shoulders, head, elbows, and wrists are all placed against the wall; the arms slide up and down while the trapezius and rhomboids are extended and contracted. (Forward neck is a result of elongated / weak trapezius and rhomboid muscles. Therefore, strengthening them should reverse the elongation.) Moreover, the lower back should be in contact with the wall, which can be achieved by contracting the abdominals. In bed, I achieve this by placing a couple of pillows under my knees, which posteriorly tilts the pelvis and flattens the curvature in the lower back. (Edit: please see my related question here about sleeping with pillows under knees.)

While lying on my bed, I noticed that if I bend my arms 90 degrees at the elbows, palms facing up, with my wrists above my head (as if I'm about to perform a wall slide but lying down on my bed), my left arm starts to go numb after a minute or so, specifically along my bicep, forearm, and part of my wrist and palm along my thumb. I think this is due to poor flexibility and, as a result, poor blood circulation. Moreover, neither of my wrists actually touches the bed (I have to press down or add a weight to get my wrists to lie flat; similarly, when I perform wall slides, I have to press my wrists against the wall since they do not lie against the wall naturally).

I'm wondering if it is okay to sleep like this and whether the numbness is something that will get better with time. Moreover, will placing my arms in the "wall slide position" overnight help correct my posture?

Answer 1

Moreover, rather than keeping my arms by my sides, I wanted to try to keep my arms in the same position they would be in when performing wall slides

But you're lying horizontally here, not against gravity. So sleeping in that position won't help much.

Also, wall slides are mainly for training upward rotation caused by the serratus anterior. To fix rounded shoulders, a much better and commonly suggested approach is to regularly stretch muscles which internally rotate the shoulder and bring them forward (pec major/minor, lats, anterior delts, subscapularis) and strengthen the scapula retractors/depressors and external rotators (rhomboids, middle/lower traps, rear deltoids, teres minor, infraspinatus) using tons of pulling exercises.

Forward neck is a result of elongated / weak trapezius and rhomboid muscles

Not really, it is probably the opposite actually. I'm guessing you might have "forward head posture" or "text neck" which means you have lost the normal lordosis present in the cervical spine (it is too straight), causing the upper trap to be in a stretched position and get weak. You should do exercises like chin tucks, which you can easily find online.

Moreover, neither of my wrists actually touches the bed

The reason is internally rotated shoulders! Tight internal rotator muscles are preventing your shoulder from externally rotating and letting the wrist touch the bed.

Moreover, will placing my arms in the "wall slide position" overnight help correct my posture?

Unlikely. If you sleep in that position, the only thing that might happen to some extent is that your subscapularis might stretch out a tiny bit due to the weight of your forearm. This does not strengthen your back musculature which is really the important part.