Sarcopenia? Never heard of it.

Chances are, the word isn't familiar, but sarcopenia is a universally experienced side effect of long life. It is the decline of lean body mass that occurs with age, the withering of skeletal muscle. It is why advanced age is often associated with frailty and it has consequences way beyond vanity and vigor. Muscle protein does more than just move you around and fill out your clothes. Muscle is the major source of protein for important functions especially when you're sick or hurt. Your body must find protein for antibody production, white blood cell production, and wound healing. If your protein reserves are low due to sarcopenia, your ability to rally when sick or hurt can be impaired.

In the past, experts thought that the natural process of protein synthesis and breakdown was impaired, as we age. New research funded by the National Institutes of Health has proven that protein metabolism is not the problem and, although you might not recognize it, this is good news. If muscle metabolism failed as we got older there would be little we could do about it. Prevention strategies can focus on things we can control--diet and exercise. Eat right, keep running and, if you don't already, add a regular program of strength training to your workouts in order to maintain vital muscle mass.

(Journal of the American Medical Association, 2001, vol. 286, No. 10, pp. 1206-1212; editorial)