Strength training may reverse muscle aging

By Amy Norton

NEW YORK (Reuters Health) - Strength training may not only make older adults' muscles stronger, but younger as well, a small study suggests.

It's well known that resistance exercises improve muscle strength and function in young and old alike, but the new research suggests that strength training also affects older muscles on the level of gene expression -- essentially turning back the clock on muscle aging.

The study, published in the online journal PLoS One, looked at whether strength training affects the "gene expression profile" in older adults' muscle. Genes hold the instructions from which the body manufactures proteins; gene expression refers to the processes that translate these instructions into proteins.

Analyzing small samples of muscle tissue from a group of healthy young and older adults, researchers found that older and younger muscle tissues differed significantly in their gene expression profiles. The difference indicated that older muscle tissue had impaired functioning in mitochondria -- structures within cells that act as the cell's "powerhouse."

That impairment was reversible, however. After 14 of the older adults underwent 6 months of strength training, the gene expression profile in their muscles showed a more youthful appearance.

"In a very real sense, the muscle was younger," said lead study author Dr. Simon Melov of the Buck Institute for Age Research in Novato, California.

Experts have long known that exercise is good for younger and older adults alike, Melov told Reuters Health, but the new findings suggest that it can "actually rejuvenate muscle" in older individuals.

The study included 25 healthy men and women older than 65, and 26 healthy adults ages 20 to 35 who had diet and exercise habits similar to the older group. By analyzing muscle tissue from each volunteer, Melov's team found age-related differences in the expression of hundreds of genes -- such that mitochondrial function in older adults appeared "dramatically impaired."

Fourteen of the older adults then went through a strength training program, working out two days a week for 6 months.

As expected, the researchers found that these volunteers boosted their muscle strength, coming closer to their younger counterparts' performance. But their muscle also showed a turnaround in gene expression that Melov described as surprisingly stark.

He said more studies are needed to see whether aerobic exercise, like walking or cycling, has similar effects on muscle -- and whether exercise might reverse molecular aging in other types of body tissue.

For now, the researchers say, their findings show that it's never too late to start exercising.

SOURCE: PLoS One, online May 23, 2007.