(HealthDay News) -- Pumping iron can literally rejuvenate seniors' muscles -- reversing the aging process within the tissue and improving people's ability to perform physical tasks, new research shows.

In the study, American and Canadian researchers examined gene expression in the thigh muscle tissue of 25 healthy older adults over age 65 (average age 70) who performed resistance training twice a week for six months. They then compared the results to tissue taken from younger adults, ages 20 to 35.

Each training session was an hour-long and involved 30 contractions of each targeted muscle group.

Reporting in the May 23 issue of the online journal PLoS One , the team found that resistance training resulted in a reversal of the "genetic fingerprint" of muscle tissue in older adults, returning them to levels that are similar to those seen in younger adults.

The study also looked at muscle strength. Before they began resistance training, the older adults' muscle strength was an average of 59 percent weaker than the younger adults. But the exercise program boosted the older adults' muscle strength by about 50 percent. That meant that by the end of six months, they were only 38 percent weaker than the younger adults.

"We were fairly surprised by the results of the study," co-author Simon Melov of the Buck Institute for Age Research in California, said in a prepared statement. "We expected to see gene expressions that stayed fairly steady in the older adults. The fact that their 'genetic fingerprints' so dramatically reversed course gives credence to the value of exercise, not only as a means of improving health, but of reversing the aging process itself, which is an additional incentive to exercise as you get older."

The researchers are planning further studies to examine whether resistance training has any genetic impact on other types of tissue (such as organs) and whether endurance training (running, cycling) affects genetics and aging.

More information

The American Medical Association has more about fitness for older adults.

By Robert Preidt
SOURCE: Buck Institute for Age Research, news release, May 22, 2007
Last Updated: April 2008
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