New research suggests running could help keep senior citizens feeling youthful.

A recent study found senior citizens who run several times per week for exercise expend about the same amount of energy walking as a 20-year-old. Those who walked for exercise instead of jogging expended around the same amount of energy walking as older sedentary older adults and 22 percent more than the average 20-year-old, the University of Colorado at Boulder reported.

The researchers believe this phenomenon occurs because mitochondria, which create chemical energy called adenosine triphosphate (ATP) that powers muscle fibers. People who exercise more often have more mitochondria in their cells, creating more muscle-powering energy.

"The bottom line is that running keeps you younger, at least in terms of energy efficiency," said CU-Boulder Associate Professor Rodger Kram of the Department of Integrative Physiology, a co-author on the new study.

To make their findings the research her looked at 30 healthy older adult volunteers, half of which were male and half female. With an average age of 69 who either ran or walked regularly for exercise. All of the participants had been participating in the exercise for at least six months, and performed the activity at least three times a week for 30 minutes per session. The subjects were asked to walk on a force-measuring treadmill at three speed: 1.6 mph, 2.8 mph, and 3.9 mph. During this activity the researchers measured the participants' oxygen consumption and carbon dioxide production.

"It was surprising to find that older adults who regularly run for exercise are better walkers than older adults who regularly walk for exercise," said CU-Boulder graduate student Owen Beck, who participated in the study. "The take-home message of the study is that consistently running for exercise seems to slow down the aging process and allows older individuals to move more easily, improving their independence and quality of life."

The findings were published in the Nov. 20 edition of the journal PLOS ONE.