Do your muscle need oxygen I lose muslce in my legs and shoulder?

Yes. Muscles need oxygen & nutrients from food to create energy to keep the cells that make up your muscles alive. The most likely reason for your muscle loss is inactivity. If you are not using those muscles, they go away. Another common reason for muscle loss is not eating enough. If your body is not getting enough calories, it takes protein from your muscles to make energy to keep your organs alive.