I went to a physio 2 days ago and now cannot lift for 2 weeks while I do rehab excercises.

My shoulder injury caused me to lose a great amount of upper body mass due to months away from heavy pressing. The only respectable body part I have left is my legs, but now taking 2 weeks off is gonna set me back again. This scares me.

What can I do to preserve as much mass as possible in 2 weeks that doesn't involve lifting heavy?