Call me a wimp if you want, but here it is Monday morning and my shoulder still is killing. Hopefully it will start feeling better so I can get the next round in. I couldn't hardly sleep last night, no matter how I laid it was throbbing.
Your shoulder getting tired is because you are trying to hold it up w/ your muscles.....It is collapsed, if you will. Drop that shoulder down and lock it in, creating a bone on bone platform. You will hold steadier and not tire as quickly. It takes a bit of practice but is much more comfortable.
Naw, my shoulder is getting tired because I tried ripping my arm off a while back by laying under my ATV. But I am not really sure what you are saying there. I don't quite get what you are saying.