No, this is not another article about why you should be active. This information tells you how exercise works to keep you healthier.

The concept to understand is called overload. And according to the government’s Physical Activity Guidelines for Americans, overload is the physical stress placed on your body when your physical activity is greater in amount or intensity than usual.

The body responds and adapts to these stresses (say, a Zumba class). For example, aerobic activity places stress on your heart and lungs and muscles. Your lungs are required to move more air and the heart pumps more blood and delivers it to working muscles. This increase in demand increases the efficiency of your lungs, heart, your entire circulatory system, and your muscles.

Muscle-strengthening exercise overloads muscles and bones in the same way—making them stronger.

Also tied to the idea of overload is the principle of progression. Once you reach a certain fitness level, you progress to higher levels of physical activity by continued overload and adaptation. These small and progressive changes help your body adapt to the additional stresses while minimizing your risk of injury.