Physicians have long recognized the health benefits of regular exercise. Now, University researchers are getting closer to explaining the ways in which exercise helps reduce susceptibility to disease.

Steve Britton, a professor of anesthesiology, and Lauren Koch, an associate professor of anesthesiology, have long bred rats to model how exercise affects the risk for developing certain diseases in humans.

“We believed that there was a strong relationship between how long one was going to live and how large their exercise capacity was,” Britton said. “It seemed that those who had a large exercise capacity were living healthier and longer.”

To test the theory, University researchers in 1996 developed a selective breeding process to generate rats that were either “high capacity runners” or “low capacity runners.” To do this, Koch said they took a large sample of rats and measured their endurance on treadmills. The rats that could run for longer periods of time were then bred together.

“We believed that if we had lab rats that we could selectively breed on low or high exercise capacity, then we could develop a model system to see how low capacity and high capacity rats harbor complex disease risks and health risks,” Koch said. “So it was a good way to look at health and disease genetically.”

Since the beginning of the breeding process more than 20 years ago, Britton and Koch have bred 36 generations of rats. Now, years of breeding are beginning to pay off — allowing researchers across the country to use these selectively bred lineages of rats to conduct their own studies. Britton said their model is the only one to allow for direct artificial selection for exercise capacity. He added that the rat model has been studied at 60 institutions nationwide, and has been the subject of about 100 papers in scientific literature.

Results from the rat model studies have confirmed researchers’ theory that exercise stimulates health and life expectancy, Britton said. The rats bred with a high exercise capacity have been shown to be more resistant to memory loss, sleep disorders, obesity and fatty liver disease compared to those bred with a low exercise capacity. In addition, their average life expectancies are between 28 and 45 percent higher.

Koch said these results are a step toward figuring out exactly how exercise benefits the human body.

“We know that exercise is good for you,” Koch said. “But we don’t know the underlying mechanisms behind it. This model is helping us uncover some of the connections between both exercise and health and inactivity and disease.”

Britton cited his collaboration with colleagues at Colorado State University as an exciting avenue for future studies. Researchers at CSU are testing the effects of exercise capacity on susceptibility to breast cancer, and their preliminary data shows rats with a lower aerobic capacity are 5.6 times more likely to develop inducible breast cancer than high capacity rats.

“We believe these studies will lead to focused translational studies for humans,” Britton said.

Nursing junior Alex Fauer, president of Michigan Triathlon, said he is optimistic the study’s results will provide even more reason to engage in regular exercise.

“The first stage of change that will make people motivated and aware to health benefits of high capacity exercise is just getting the data out there,” Fauer said.

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