Nov 20, 2014 09:11 PM EST By J Baulkman, UniversityHerald Reporter

A new study suggests that running regularly could help older adults stay young.

Researchers from the University of Colorado at Boulder and Humboldt State University found that senior citizens who run several times a week for exercise expend about the same amount of energy walking as a typical 20-year-old.

"The bottom line is that running keeps you younger, at least in terms of energy efficiency," Rodger Kram, co-author on the new study, said in a statement.

For the study, researchers collected data from involved 30 healthy older volunteer adults (15 males and 15 females) with an average age of 69 who either regularly ran or walked for exercise. The volunteers all had been either walking or running at least three times a week for a minimum of 30 minutes per workout for at least six months.

"What we found is that older adults who regularly participate in highly aerobic activities - running in particular - have a lower metabolic cost of walking than older, sedentary adults and also lower than seniors who regularly walk for exercise," Justus Ortega, who led the study, said in a statement. "It's been known for a long time that as people age their maximum aerobic capacity, or 'horsepower,' declines, and that is true for runners as well. What's new here is we found that old runners maintain their fuel economy."

All study participants underwent preliminary health screenings at the CU-Boulder Clinical and Translational Research Center (CTRC), which is funded primarily by the National Institutes of Health.

The test subjects walked on a force-measuring treadmill at three speeds in Kram's Locomotion Laboratory at CU-Boulder: 1.6 mph, 2.8 mph, and 3.9 mph. The researchers measured each participant's oxygen consumption and carbon dioxide production during the testing sessions. For the new study, the team also used data gathered as part of Ortega's dissertation on the energy expended by younger and older sedentary adults during similar walking treadmill tests for comparison.

"Walking for exercise has many positive health effects, like fending off heart disease, diabetes, weight gain and depression - it's just that walking efficiency does not seem to be one of them," Kram said. "Because we found no external biomechanical differences between the older walkers and runners, we suspect the higher efficiency of senior runners is coming from their muscle cells."

Specifically, Kram believes that mitochondria -- small bodies found inside individual cells known as the cell "powerhouses" -- are involved. Mitochondria generate chemical energy known as adenosine triphosphate (ATP) that powers our muscle fibers to help us move about, lift objects, and, in this case, run. People who work out regularly generally have more mitochondria in their cells, providing more energy to power larger muscles.

Kram said further research is needed to determine the role mitochondria play in the energy efficiency exhibited by running seniors.

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