From the Seinfeld episode The Summer of George:
Doctor: Mr. Costanza...your legs have sustained extensive trauma. Apparently your body was in the state of advanced atrophy, due to a period of extreme inactivity.
But with a lot of hard work and a little bit of luck, I think there's a good chance you may, one day, walk again.
From an article in today's WSJ called Watching TV Linked To Higher Risk of Death:
In a provocative look at the impact of sedentary behavior on health, a new study links time watching television to an increased risk of death.
The results are supported by an emerging field of research that shows how prolonged periods of inactivity can affect the body's processing of fats and other substances that contribute to heart risk.