This is how the body’s desire for homeostasis can be harnessed to drive changes: push it hard enough and for long enough, and it will respond by changing in ways that make that push easier to do. You will have gotten a little stronger, built a little more endurance, developed a little more coordination. But there is a catch: once the compensatory changes have occurred—new muscle fibers have grown and become more efficient, new capillaries have grown, and so on—the body can handle the physical activity that had previously stressed it. It is comfortable again. The changes stop. So to keep the
...more
