Originally Posted by Mr. Death
The reason you can't move your shoulder probably has nothing to do with your workout, it is because you injected there for the first time. Also, you will not see significant gains from injecting in different areas like your source said. All of your gear goes to the same place ( your bloodstream) no matter where you inject. However, it is good to switch injection sites to keep from building up scar tissue. If you want to workout an area on the same day you inject into it, that is up to you. It just depends on whether or not you feel it affects your ability to workout at your fullest.