AS AMERICANS, we tend to believe that if a little is good, more must be better. This belief is deeply entrenched in our national psyche, and it's especially true when it comes to cardiovascular exercises like running.

In America, running is considered the King of Exercise.

After all, running is good for your cardiovascular health, aiding in the prevention of diseases such as heart disease, diabetes and obesity, right? Doesn't running increase bone density and help you live longer, too?

That may not be so, especially if you're over 35, according to scientific research published this month in the British journal Heart.

According to the report, "extreme endurance exercise may exact a toll on cardiovascular health . . . cause excessive 'wear-and-tear' on the heart, inducing adverse structural and electrical remodeling, which offsets some of the [cardiovascular] benefits and longevity improvements conferred by moderate physical activity."

In short, daily, extreme exercise may be doing more harm than good, erasing many of the health benefits you seek.

What's extreme? According to the report, which followed about 53,000 people for 30 years, those who ran more than 20 to 25 miles a week (2.8 to 3.57 miles a day) lost their longevity advantage.

Finally, I've been vindicated!

I have always opposed extreme exercise and have always preached moderation. For years, I have watched friends and colleagues who were hard-core runners or participants in extreme sports get banged up with injuries - sometimes permanent ones. I know of two cases of premature death involving high-intensity athletics.

Of course, some critics will vehemently dismiss this new data as mere hyperbole - the likelihood of consensus on this issue is probably slim. To those critics, I say, remember Jim Fixx, author of the 1977 best-seller The Complete Book of Running, which many say initiated our national love affair with that sport. Poor Jim died from a heart attack after a daily run in 1984. He was only 52.

There's no need to run yourself into the ground. The key is to age gently, gracefully, with minimum to no damage to yourself. In the end, once again, it is the tortoise and not the hare that wins the race.

Have a question or a different viewpoint on this issue? Let's discuss. Tweet me @fit_mama#exercisingrestraint.

Kimberly Garrison is a wellness coach and owner of One on One Ultimate Fitness in Philadelphia. Email her at kimberly@1on1ultimatefitness.com. Her column appears Wednesdays.