We all know that exercise is good for us. It boosts circulation and tones the cardiovascular system. It builds strength, burns calories and reduces depression. It improves insulin sensitivity in people with diabetes. It may even help delay the onset of Alzheimer's disease. But here's what you didn't know: it can partially reverse aging at the cellular level.
A study appearing this week in the online journal PLoS One looks at the effects of six months of strength training in 25 elderly volunteers aged 65 and older (average age: 70). The researchers took small biopsies of thigh-muscle cells from the seniors before and after the six-month period, then compared them with muscle cells from 26 young volunteers (average age: 22). "To be honest, we were expecting some indication that the exercise program improved strength," says biologist Simon Melov, director of genomics at the Buck Institute in Novato, Calif., and coauthor of the study. What the scientists didn't expect was what they actually found—that after six months of resistance training, there were dramatic changes at the genetic level. As Melov puts it, "The genetic fingerprint [of the elderly participants] was reversed to that of younger people—not entirely, but enough to say that their genetic profile was more like that of young people than old people."
What kind of workout routine does it take to produce these changes? The seniors went through a rigorous exercise program—an hourlong session of strength training twice a week for six months, using the same types of machines found in most gyms. At each session, they performed three sets of 10 contractions for each muscle group, similar to a standard workout (albeit using lighter weights than most young people would use). Trainers and kinesiologists were on hand throughout to make sure the participants used the machines properly and did not injure themselves. It helped that all the participants were in good shape to start with—able to go shopping, walk the dog, play golf or swim. That was deliberate, according to Dr. Mark Tarnopolsky of McMaster University in Canada, who headed up the clinical portion of the trial. The researchers wanted to zero in on genetic changes related to aging itself, not changes that might be due to cancer or heart disease.
And how did the genes change? At the beginning of the six-month period, Melov found significant differences between older and younger participants in the expression of 600 genes, indicating that these genes become either more or less active with age. By the end of the six months, exercise had changed the expression of a third of them. Admittedly that leaves two thirds of the genes unchanged. "The others appear to be related to aging, but not exercise," says Melov. But he was struck by a common feature of the ones that did change. Overwhelmingly, they are involved in the functioning of mitochondria, the powerhouses of cells, which process nutrients into energy.
You might expect that, as a result, the participants had more energy—and that's exactly what they reported. "Anecdotally, some reported that before the training, they had a hard time picking up their grandchildren," says Tarnopolsky. "Afterward, they could pick them up." Others reported that it became easier to carry heavy grocery bags or run up the stairs. And objective measurements showed that their strength improved by 50 percent. For Barbara Ford, 72, of Hamilton, Ontario, the real thrill came when her grandchildren came to visit and admired her new biceps. "They thought it was a scream I was getting 'Popeye muscles'," she says. "When they saw this, they all laughed."
The take-home message is clear. "It's never too late to start exercising," says Tarnopolsky. You're only as old as your genes.