The original discovery in 2009 was so significant that the researchers all became Nobel Laureates. What they determined was the tiny pieces of DNA at the ends of chromosomes called telomeres had a job similar to aglets, the plastic or metal sheaths at the ends of a shoelace.

In the same way aglets keep laces from fraying as they are pushed through a shoe's eyelets, telomeres keep the active ends of chromosomes from being exposed.

You don't want the active ends of your chromosomes exposed! Exposure makes cell division impossible, which means when a cell dies, it can no longer replace itself.

Healing stops. Aging starts.

So telomere length is a way to estimate biological age. Subsequent research found something that seemed to retain telomere length as people aged: exercise.

Really intense, long-term exercise.

German researchers compared the telomere length of long-term, vigorous exercisersrunners the average age of 51 who had been averaging 50 miles a week since they were young with healthy nonexercisers of the same age and found that the runners' telomeres were more than 40 percent longer than those of the healthy nonexercisers.

Dr. Christian Werner, an internal-medicine resident at Saarland University Clinic in Homburg who worked on the project said, it was "striking" to see "that many of the middle-aged athletes looked much younger than sedentary control subjects of the same age."

Another striking finding in this study was that when the middle-aged megamilers were compared to runners on Germany's national track team runners primarily in their 20s! their telomere length was nearly the same.

Moreover, two other studies of twins showed the one who exercised regularly had longer telomeres than the one who didn't.

But running 50 miles a week for virtually your entire adult life isn't feasible for most people, so the next research research goal became to determine if lesser amounts of exercise would produce similar results.

So Dr. Elizabeth Blackburn, one of the original 2009 Noble Laureates worked with other researchers at the University of California and devised a study that had 62 postmenopausal women assess their degree of stress for a month before they logged their amount of exercise time for three days. Through the use of periodic blood tests, the length of the women's telomere length was measured in their immune cells.

What was found was that the women who had engaged in at least 42 minutes of "vigorous activity" defined to them as "increased heart rate and/or sweating" during the three days had less shortening of the telomeres.

Equally as important was the discovery that this amount of exercise not only combatted the overall effects of aging but also those specifically caused by psychological stress.

Prior to this study, another on premenopausal women showed that psychological stress shortened the length of the telomeres in immune cells.

But in this study, only the women who were characterized as inactive and under a great deal of stress had shortened telomeres. The women under a great deal of stress who had engaged in at least 42 minutes of vigorous exercise over the three-day-period didn't.

As a result, you now have one more compelling reason to exercise.

For years, we knew that exercise was an effective way to combat the mental fatigue produced by stress, but this latest research now shows that it alleviates the physical toll as well.

To close, consider that the cover story of the May issue of Consumer Reports on Health cited 10 benefits to exercising 30 minutes a day most days of the week: lower blood pressure, better balance (which reduces the risk of falls and broken bones), a reduced risk of cancer, an increase in bone strength, improved cholesterol levels (the LDLs go down and the HDLs go up), improved mood, a lessening of joint pain, a better quality of sleep, a better quality of sex, and last but far from least weight loss.

Yet the 2008 Summary of Health Statistics of U.S. Adults: National Health Interview Survey determined that "when considering all leisure-time physical activity, 36 percent of adults were considered inactive," and "59 percent of adults 18 years of age and over never engaged in any periods of vigorous leisure-time physical activity lasting 10 minutes or more per week."

So what's more amazing: the benefits of regular exercise or that more adult Americans don't avail themselves to them?

Especially now when we know it battles both the mental fatigue and the physical damage caused by psychological stress.

And for those of you who do not think that life is more stressful than ever before, consider how the degree of stress has increased in just one area: the workplace. According to a 2009 survey done by CareerBuilder.com, 37 percent of the 4,400 polled claimed to be doing the work that used to be done by two people, 34 percent are spending more time at the office, and 22 percent are working more weekends.