You may recall the sad story of Grete Waitz, the nine-time champion of the New York City marathon and Olympic medal-winner, whose career as a runner may have played a huge hand in her continuing struggle to fight cancer. You might also remember Jim Fixx, a marathoner and author of "The Complete Book of Running," who died some two decades ago of a heart attack at the age of 52 -- while he was running.

Now don't get me wrong. I am a major fan of exercising and have been an active runner for nearly 40 years. However, I just don't want people to make the same mistake I made when I started my exercise program.

It is very easy to get caught up in the philosophy that if a little bit is good then more is even better. Unfortunately, this logic rarely is true, and with exercise, I believe there is compelling evidence to suggest otherwise.

Exercise is a form of destructive stress and it tears your body down. But we absolutely need it to rebuild and repair because your body is in a constant flux or dynamic of repairing and rebuilding.

However, what most people fail to understand is that it is easy to overdo exercise. Although it is common knowledge that too much of a good thing can be harmful for you, exercise is clearly no exception to this rule. The vast majority of people in this country are severely underexercised, but it is possible to overdo it and actually harm yourself.

What you really need is a combination of endurance and anaerobic sprinting or strengthening exercises that help to increase the instantaneous and dramatic demands on your cardiovascular system and prevent heart attacks.

Just one more reason, among many, for treating exercise like a drug that must be prescribed precisely to do the most good.

On Vital Votes, reader Judy from Albuquerque, New Mexico argues in favor of moderation:

"I feel that everything we do must be done in moderation.  That includes exercise.  It stand to reason that if you exercise to the extreme, you will deplete your energy reserves and will soon be run-down.  In this state, it is easy for diseases to get a foothold. That is a real no brainer.  We also need to remember that we are all different.  What is extreme for me may be moderate for someone else.  Listen to your body and do what feels right for you -- not someone else, even if that someone else is an 'expert'."

Other responses to this article can be viewed at Vital Votes, and you can add your own thoughts or vote on comments by first registering at Vital Votes.