Länk - Sporta - men inte för hårt

Lean mass in general is one major defining predictor of longevity. The concept of dying of "natural causes" is, in reality, better described as "dying from organ failure due to loss of organ reserve and lean tissue." Organ reserve (the functional capacity of any or all organs necessary to support life) and skeletal muscle mass tend to increase or decrease together depending on the stimulus or lack of it.

So, as a rule of thumb, anything you do to build muscle generally tends also to build or improve other tissue, including vital organs (heart, liver, lungs, kidneys, etc). Similarly, anything you do to diminish muscle tends likewise to have a negative effect on organ reserve. We call it "atrophy." Of course, the old adage "use it or lose it" has significance here, since it is presumed that by moving about, by doing work and generally being "vital" you give your body a reason to "adapt" to the work.

Furthermore, because your muscles are generally fed either directly or indirectly by those organs, they are also called upon to adapt and stay vital. Stay in bed for a few weeks and you'll lose both muscle mass and organ reserve. If you are young, you can build both back with diet and minimal exercise. If you are old, it's often the beginning of the end.