Endurance athletes sometimes say they're "addicted" to exercise. In fact, scientists have shown that rhythmic, continuous exercise — aerobic exercise — can in fact produce narcoticlike chemicals in the body.

Now researchers suggest that those chemicals may have helped turn humans, as well as other animals, into long-distance runners.

The man behind the research is University of Arizona anthropologist David Raichlen, a runner himself. He does about 25 miles a week.

When it comes to walking, the easy part is understanding the benefits: Regular, brisk walks can strengthen our bones, help control blood sugar, help lower blood pressure and cholesterol, and the list goes on. The hard part is finding the time to fit it in.

Engineering physical activity back into Americans' daily lives is the goal of an educational campaign launched by Kaiser Permanente,an Oakland, Calif.-based health plan.

Somewhere on the path to the White House this year, a powerful set of ideas began to creep into the mainstream debate over which direction the country will take.

These are ideas that not too long ago were written off as marginal, or even worse, a little kooky. They come from Libertarians: free and open markets and extremely limited government. Those ideals are now becoming more mainstream and are influencing the Republican Party.

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(SOUNDBITE OF CLOCK TICKING)

GUY RAZ, HOST:

She closed the book, placed it on the table and finally decided to walk through the door. That's the starting sentence for Round 8 of Three-Minute Fiction. That is our contest where we ask you to write an original short story that can be read in about three minutes. We are no longer accepting submissions for this round.

Our readers from across the country are almost done going through all of the more than 6,000 submissions this round. So let's hear a few samples of their favorites so far.

Transcript

GUY RAZ, HOST:

This past week, charges were filed against members of the Florida A&M marching band in the hazing death of a former member. In recent weeks, there have been a string of hazing scandals on campus. In April, five Boston University students were bound and beaten in a fraternity house basement. And Rolling Stone magazine recently profiled a Dartmouth student's humiliating hazing experiences.

But as New Hampshire Public Radio's Dan Gorenstein reports now, all of this attention may be a good thing.