Exercise not only makes skin appear younger, but according to a surprising new study, exercise can reverse the aging of people’s skin even when they start exercising at a later age. Many of us have noticed from our own tragic experiences that as time passes, our skin changes, with wrinkles, crow’s feet and sagging. This is caused by changes in the internal layers of the skin. After the age of forty, the stratum corneum, the most superficial layer of skin that plays a defining, protective, outermost layer, begins to thicken in most people. The stratum corneum is this part of the skin that you can see and touch. It is made up mostly of dead skin cells and some collagen, and as we age, the stratum corneum will become drier, easier to shed, and more dense in texture. At the same time, the layer of skin below the stratum corneum, known as the dermis, begins to thin. It gradually loses cells and elasticity, making the skin clearer and more flabby from the outside. These changes are not related to skin damage caused by sun exposure, but are purely the result of aging. Recently, however, researchers at McMaster University in Ontario, Canada (McMaster University) have begun to wonder if these changes are really inevitable. Early research at the university found that early signs of aging in mice that had been bred to show premature aging could be slowed or even disappear if they were kept in motion. In contrast, when such mice remained stationary, they rapidly became dry, thin, frail, sickly, mentally deranged, and had graying or loss of hair. However, compared to their stationary counterparts, the mice that had the opportunity to exercise on the wheel kept their brains, hearts, muscles, and reproductive organs healthy and their hair longer. Their hairs never even turned white. Of course, a long time ago, our human hair was replaced by bare skin. However, the researchers speculated that if exercise could keep animals from aging in appearance over time, then it could have the same effect on our skin. To confirm this possibility, the researchers first recruited 29 volunteers, who lived locally and were between the ages of 20 and 84, both male and female. About half of the participants usually like to exercise, at least three hours of moderate or vigorous exercise per week, and the other half were very quiet, exercising for less than an hour per week. Then, the researchers asked each volunteer to expose half of his or her buttocks. “We wanted to examine skin without frequent sun exposure,” said Mark Tarnopolsky, MD, PhD. He is a professor of pediatrics and sports medicine at McMaster University and the study’s leader. The study was presented this month at the American Medical Society’s annual sports medicine meeting in New Orleans. Researchers biopsied skin samples from each volunteer and looked at them under a microscope. When compared strictly with age, the skin samples generally met expectations. Older volunteers typically had thicker skin on the surface and thinner skin on the inside. But when the researchers went a step further and subdivided the volunteers’ samples by exercise habits, the results issued a significant change. They found that after reaching the age of 40, men and women who exercised frequently had significantly thinner and healthier epidermal layers of skin and thicker dermal tissue. Their skin was closer to the 20- or 30-year-old age group in terms of composition, and differed significantly from the same age group, even past age 65. But the researchers realized that other factors, including diet, genetics and lifestyle, may also have influenced the skin differences between the fitness group and the sedentary group. It was almost impossible to confirm whether it was the exercise itself, or lucky genetics or a healthy life that influenced the state of people’s skin. So the researchers then set up another group to get the group moving after collecting skin samples from the buttocks of sedentary volunteers. In the initial phase of the study, the skin of this group of volunteers over 65 years of age was consistent with their age. Then began a very brief endurance training session, practiced twice a week, running or cycling at a moderately strenuous pace and exercising continuously for 30 minutes at a level of at least 65% of their maximum aerobic metabolic capacity. Such training continued for three months, after which the researchers again biopsied their skin. But at this point, their skin samples looked all different, with both the outer and inner skin layers looking close to those of people in their 20s and 40s. “I don’t want to exaggerate the results of the study, but really, it looked just amazing,” said Dr. Tarnopolsky, who is himself middle-aged and often athletic. “Under the microscope, the volunteers’ skin ‘looked a lot younger, and the only thing they changed was that they started exercising.'” How exercise changed the skin composition is not entirely clear, but in a separate part of the study, the researchers examined changes in the levels of a specific substance created as a result of muscle work. The substance, called muscle hormones (myokines), is now known to enter the bloodstream and initiate changes in the cells rather than the muscles themselves. In the study, researchers found that after exercise, volunteers showed a significant increase in the amount of a muscle hormone called IL-15 in their skin samples. After three months of exercise, the amount of IL-15 contained in their skin samples increased by nearly 50 percent from the initial phase of the study. The researchers suspect that the increased muscle hormone is also linked to exercise-related skin changes, and for this reason, Dr. Tarnopolsky said, it is also unlikely that any IL-15 capsules, creams or injectable shots could replace the skin benefits of exercise. At the same time, there is no evidence that exercise can erase wrinkles and other damage from sun exposure, and some of that damage may be caused by the accumulation of outdoor exercise over time. Still, Dr. Tarnopolsky said, “It’s amazing to think that exercise changes our bodies in such intricate ways,” and that variety of changes includes the skin in gym shorts.