How old is your body?

New research suggests that your body parts age at different rates. The good news: Exercise turns back the clock.

We’ve all heard of the marathoner with the heart of a nineteen-year-old, or the yogi whose backside seems to be decades behind the rest of her. But is there any truth to these statements? Maybe so. According to a recent study out of UCLA, certain tissues and organs do age at different rates than others. Healthy breast tissue, for example, was found to be about two or three years older than the rest of a woman’s body, while heart tissue appeared to be, on average, about nine years younger than everything else. Although the exact cause for these variations is still unknown (essentially, it’s in our DNA), there are research-proven ways to help keep your body as young, vibrant and healthy as possible. “We’re dealt a certain genetic hand, but what we do over the course of our lives can modify that,” says Equinox Advisory Board member Thomas Storer, Ph.D., director of the exercise physiology laboratory at Brigham and Women’s Hospital in Boston. Here’s how to help physically turn back the clock on all your different parts.

Heart and Lungs: Master athletes who continue training as they get older lose their cardiovascular fitness at about half the rate of their couch potato peers, says research published in the Journal of Applied Physiology.Another study, published in the journal Circulation, revealed that six months of endurance training reversed any and all age-related declines in aerobic power that study participants (men in their 50s) had experienced. “You need to stay active to keep everything working properly, but you also need to build in plenty of recovery time,” says Equinox Advisory Board member Justin Mager, M.D., an exercise physiologist and internist in Mill Valley, California. “Your heart actually works 1/3 of the time, and the other 2/3, it’s recovering for the next beat. Similarly, it’s very important to give your body time to adapt to change and stress.”

Muscles: According to the American College of Sports Medicine, starting at around age 40, our muscle performance deteriorates at a rate of about 5 percent per decade, with the process speeding up after age 65 to 70. But research published in The Journal of Clinical Endocrinology & Metabolism shows that you could potentially slow (or reduce) that muscle loss by following a consistent cardio and strength program, even if you don’t start until later in life.

Joints: Being smart about your biomechanics will pay off over time. “If you have knock-knees when you run, or your back is mal-aligned on the bike, or you regularly perform exercises improperly at the gym, the continued aggravation you cause your body will create pain, arthritis, and ultimately age your joints more quickly,” says Storer. “Receive proper training, and follow proper technique, and you’ll be in it for the long haul.”

Breasts: While the study findings mentioned above pertain more to hormonal differences in breast tissue, the undeniable sagging that occurs to breasts over time is due in large part to the deterioration of the Cooper’s Ligament, which goes across the breast. “If a woman who does high-impact activities tries to reduce movement with solid support, the speed at which the ligament breaks down would be slower,” says Storer.

Cells: Every cell, or chromosome, in your body is capped with a telomere, or a stretch of DNA that makes it possible for cells to divide. Each time a cell divides, telomeres get shorter, and over time, when they get too short, they die. Therefore, researchers often use the length of telomeres to assess biological aging. One German study compared the length of middle-aged long-distance runners’ telomeres with those of sedentary people the same age, and the results revealed that the runners’ telomere loss was reduced by about 75 percent, meaning that their actual cells were significantly younger than their inactive peers. Long live marathoners—quite literally.