deconditioning
Our internists use this also, but they want us to code 780.79. Sounds like everyone has their own idea of what this is. So, I looked up the definition:
de·con·di·tioned, de·con·di·tion·ing, de·con·di·tions
v. tr.
1. Psychology To cause (a conditioned response, such as a phobia) to become extinct.
2. To cause to decline from a condition of physical fitness, as through a prolonged period of inactivity or, in astronauts, through weightlessness in space.
v. intr.
To lose physical fitness.