All of this emerged out of his study of the mitochondria (energy-producers inside cells) in mice. In one set of mice with defective mitochondria, their skin aged dramatically if they were sedentary. But with regular exercise, the mice looked normal, without the aged skin. So he studied humans. He found exercise helps us overcome mitochondrial defects, too. The lesson here is that keeping an active life style with vigorous exercise on a regular basis will make you and your skin look younger.