During recovery from my pyeloplasty, I've been making use of a technique recommended by my swim coach. He told me about the Carpenter effect (a.k.a. the Ideomotor effect.) If you check out the Wikipedia entry on the topic, you'll find an explanation of the phenomena but not exactly as my coach described it.
He explained that - while not yet scientifically proven - people who mentally train while physically incapacitated lose less muscle mass during their convalescence. I've been giving this a try. In my mind, I go through three sets of twelve reps for all the major muscle groups and imagine that I'm training to failure at the end of the third set. I haven't had any muscle soreness the day after but if nothing else, I'm super relaxed after my "session" is done.