alt Hacker NewsI can speak anecdotally, at least.
My shoulders are pretty wide for my frame. When using most laptop keyboards and many standard keyboards, I have to tuck my shoulders in and twist my wrists. This was causing some serious pain and tension in my neck, shoulders, and wrists, likely leading toward carpal tunnel.
I made two different changes in succession that helped greatly (and I don't remember the order now):
1. With a split keyboard, the halves could be placed so my wrists are straight and my arms hold at shoulder-width, and this rapidly reduced the amount of tension I was experiencing and gradually eased my wrist issues. Tenting the keyboard and getting a vertical mouse helped as well, but I'd rate those as minor improvements, especially since I aim not to drive with the mouse as much.
2. With Colemak layout, I was able to gradually transition from QWERTY (there's a series of AHK scripts I found at the time that basically rotated triples of keys). This helped reduce wrist strain at the hand level.
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Another shoulder anecdote... I also really appreciated being able to open up my shoulders.
I was once amused by a friend that had never seen a split keyboard before - they were mostly delighted with having a place to put their coffee...
The shoulder problem was similar for me.
For many years I have used very cheap Microsoft ergonomic keyboards (discontinued some years ago), which were already much better for the position of the arms than standard keyboards.
Then I switched to a truly split keyboard, which is even better.
I have also switched to Dvorak a few years ago. A couple of months were needed until recovering and then exceeding the previous typing speed, but it was worthwhile, because the comfort of typing has greatly improved. Now I regret that I have not done this earlier.