Exercise keeps our bodies and all of their parts working efficiently. When your heart is fit, it beats more strongly but uses less energy to keep pumping. When your muscles are fit, they can lift more and work longer without feeling stress or getting hurt. When your entire body is fit, you burn more calories, sleep better at night, and have a stronger immune system. When you exercise regularly and effectively, your body is lean, sleek, and capable. A fit body takes up less room than an unfit body, but it is able to do far more.