Maintaining Muscle Mass During Injury

Hi I have a shoulder Injury between my upper biceps and my shoulder junction on the left side, It is a muscle injury and the doctor said it will take 3 weeks, It has been more than 3 week getting better but still not fast enough and I canâ??t train it .
The Injury prevents me from doing any chest press or over the head press and biceps curls. I can do pull movements cable for triceps but thatâ??s it.

I NEED HELP!!! I lost tons of hard work muscle on the upper body Biceps and chest. I worked so hard to gain. I was doing only legs work outs 3 times a week for the last 3 weeks, but got over trained I lost muscle and my fat percentage went up 3 percent up!!. I kept my cardio to 3 times a week in between 25 min intervals.

Is there anything I can do to keep my upper body gains even a little bit?
What about lower body /legs can I do them 3 times a week plus aerobic without burning them out?.
Thank you

Not stressing about it will go along way to prevent cortisol spikes from catabolizing the muscle.

3-6 weeks is nothing over the course of a lifting career. You will definitely gain that muscle back when you are healthy.

I’ve had a moderate muscle strain before. I gave it complete rest for 2 weeks then I slowly started adding resistance. Never took it to failure. I have no idea if it helped me heal faster but after 4 weeks I was pretty much good to go.