What is physical fitness? A condition or state of being that helps you look, feel and do your best. It is the ability to do tasks full of energy, and still be able to do other things with your time, such as schoolwork and activities with family and friends. It is a basis for good health and well being. Fitness involves performance of the heart and lungs, and the muscles of the body. Fitness can also influence how alert you are and how you feel emotionally.