I’ve seriously aggravated the muscle groups in my left shoulder, particularly around the scapula. You would think this would be a problem for my left shoulder. So would I, but apparently it’s also a problem for my entire torso.
I’m serious. Doing ANY large motion (even if I let the left arm hang completely loose) causes spikes of pain easily on part with being stabbed in the back. I would know, having had some experience with being stabbed.
Remember: evolution comes up with solutions. That doesn’t necessarily mean those solutions are good. For example, nerve endings. I think I’m going to lie down again.