“As we age, daily hours of minimal physical activity—typically in chairs—render us more vulnerable to a litany of chronic illnesses and disabilities that used to be rare or unknown such as heart disease, hypertension, many cancers, osteoporosis, osteoarthritis, and Alzheimer’s. It is commonly assumed that these conditions are the inevitable by-products of more of us living to be older. But this is not entirely true. Exercise may not be an elixir, but by stimulating growth, maintenance, and repair, it can reduce our susceptibility to many of these mismatches. In this sense, exercise is medicinal. And unlike other medicines, exercise is free, has no side effects, and is sometimes fun. So to stay healthy and fit, many of us exercise.”