Heavy arms

Why are my arms becoming heavy when I lay down?

[Cleveland Clinic]

I am not sure this is cardiac related at all. Arm pain or heaviness related to cardiac disease usually occurs in the setting of exertion not recumbency. It may be related to the different set of muscles required to move the arms in this position ( anterior deltoid) versus the group of muscles used when you are standing.

[3dragons]

Could it be related to the type and intensity of activity that you do when you are not lying down? As a fitness instructor, I used to lead a very physical day. I didnt feel tired during work because I was on the go, but when it came to lying down and relaxing, not having to push through what I had to do, my whole body felt heavy, particularly my limbs. It is amazing what we dont feel when we are on the go, so it is probably an obvious question, but just wondering none the less.