henry copeland:

Take a Vacation From Exercise? Your Body May Not Thank You - The New York Times

Like the adults in the other study, these older volunteers quickly developed worse blood sugar control during their two weeks of barely moving. Insulin resistance climbed. Some developed changes in muscle tissue indicating that they might soon begin to lose muscle mass, and a few had to be removed from the study because they had edged into full-blown Type 2 diabetes after becoming inactive. For most of the men and women who remained in the experiment, their undesirable metabolic changes were not fully reversed after two weeks of moving about again.
- www.nytimes.com