working out, arms go to sleep. why?

I’ve been working out recently, and did so last year for a while. I notice now (and previously) that when I wake up from sleeping my arm(s) is asleep; like the circulation has been cut off to it. I wake up with my arm curled across my chest, like I have always done.

I’m pretty sure its related to my working out, and I’m not really worried about it medically. I was just wondering why this is happening; and will it perhaps go away after a while.

IANAM.D., but it sounds to me like it could be thoracic outlet syndrome. In English, all the nerves and blood vessels that serve your arm have to pass through the comparatively narrow area where it joins your chest. Tight chest muscles, especially the pectoralis minor, can constrict the main nerves serving your arm. Ask a physical therapist and if they confirm TOS, they’ll most likely prescribe stretching exercises to loosen things up.

Ditto the idea of a pinched nerve. Limbs falling asleep has to do with cutting off the nervous supply, not the circulation. If you cut off the circulation, you’d wake up with a dead, necrotic limb.

See a physical therapist.