When we exercise, our hearts beat faster and harder, which makes our hearts stronger. 

When we do weight-bearing exercise, our bones are strengthened, as are our muscles. 

When we exercise, we strengthen the muscles around our lungs, and we move oxygen briskly through our bodies.

When we exercise, our organs of digestion work smoothly to move food through.

Let's look more closely at the effect of exercise on each of these organs.