Just to put the much posted "old man" picture of Arnold into perspective:
When I was 27 , I came down with severe appendicitis that required a 10 day hospital stay. In those 10 days, I lost 17 pounds and had trouble walking when I got out. I needed to use a cane! My wife joked that I looked like an old man. At the time I was a competitive bicycle racer, at an extremely low bodyfat level. I finished top ten in a 100 mile race the week before the hospitalization. A month after, I struggled finishing a 25 mile event, very near last.
Now crack open your chest, put in some valves and get told that you shouldn't do anything strenuous for about 3 months. It takes a major toll on your body in a very short time.