Alternative exercise recommendation while healing?

I got involved in a bike crash on the weekend. While the bike and myself are OK, I do have a few abrasions on/near my knee. The doctor said I need to minimize my movement if I want to heal fast - which means I have to take a break from the saddle. In the mean time, I am think of strength training for my upper body. I really feel bad I miss the training to prepare my charity ride.