On a running high

On a running high

One runner eagerly heads out the door for a 10-mile run, while his or her neighbor is done after 1 or 2 miles — or skips the run completely in favor of enjoying a cup of coffee.

It's hard to say exactly why some people are motivated to exercise more, or more often, than others. But a University of Illinois researcher has found some clues about how changes in the brain might affect motivation.Blog Photo

Justin Rhodes is a neuroscientist with the Beckman Institute for Advanced Science and Technology. He is involved with a study of mice who are bred to be highly addicted to running.

Researchers initially thought that the changes they would notice first in the mice would be in their muscles and lung capacity, Rhodes said. Instead, the changes happened in the animals' brains.

"What we discovered was they looked like an animal addicted to drugs," Rhodes said.

He and other researchers found that the dopamine system in the brains of the specially bred mice were altered so the mice perceived more pleasure from running or they wanted to do it more. It is a similar change in the dopamine system found with ingestion of drugs such as cocaine. The mice bred to run more experience a stronger reward via the dopamine system than regular mice.

The mice are part of a long-term experiment that started 25 years ago. Mice that liked to run more were bred to each other, and over time that produced mice — now the 80th generation in the experiment — who were long-distance runners. Rhodes said all animals will run for pleasure, and regular mice might run 2 to 7 kilometers per day. But the mice bred to really love running would run 15 to 30 kilometers per day on their exercise wheels.

Blog Photo"They don't need to run to get their food. They don't need to run to get their water. They're running for their own pleasure," Rhodes said.

If the mice who love running are kept from it, they experience brain patterns that show withdrawal symptoms similar to those of drug withdrawal.

Some of the other findings involving the mice showed the ones who were bred to run more didn't necessarily spend a lot more time running, but they ran faster than regular mice and so ran more miles. Over generations, their bodies changed as well as their brains. The long-distance running mice developed smaller skeletons and leaner bodies, with thinner muscles and less body fat, even though they ate more. Their limbs were also more symmetrical.

"First they became exercise addicts, then they became athletes," Rhodes said.

Rhodes and his research team recently identified a specific gene that alters the dopamine pathway of the mice and makes them want to run more. Perhaps it will someday be possible to duplicate that change in physiology with a pill that would increase a person's motivation to exercise.

In the meantime, however, it is up to the individual to put on the running shoes and get out the door.

"I don't know yet about how to motivate people to exercise, at least not with chemistry," Rhodes said.

But other information researchers have learned about exercise and the brain might help. Rhodes noted that it is well-established that exercise helps maintain cognitive ability, enhancing memory and learning.

"That much we know. There's a lot of really compelling evidence," Rhodes said. "Your brain is the most valuable thing you're going to lose" if you're not active.

That's a powerful motivation to get moving.

Jodi Heckel, a writer for the University of Illinois News Bureau, is a runner, swimmer and triathlete. You can email her at jheckel@news-gazette.com, or follow her at twitter.com/jodiheckel. Her blog is at http://www.news-gazette.com/blogs/starting-line/.

Photos: Top, 2014 Christie Clinic Illinois Marathon participants cross from Champaign into Urbana at Wright Street. Photo by Holly Hart/The News-Gazette. Bottom: Justin Rhodes.


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