Physical fitness is most easily understood by examining its components or "parts."
There is widespread agreement that these four components are basic.
1. Cardiorespiratory Endurance: the ability to deliver oxygen and nutrients to tissues, and to remove wastes, over sustained periods of time. Long runs and swims are among the methods employed in measuring this component.
2. Muscular Strength: the ability of a muscle to exert force for a brief period of time. Upper-body strength, for example, can be measured by various weight-lifting exercises.
3. Muscular Endurance: the ability of a muscle, or a group of muscles, to sustain repeated contractions or to continue applying force against a fi xed object. Push-ups are often used to test endurance of arm and shoulder muscles.
4. Flexibility: the ability to move joints and use muscles through their full range of motion. The sit-and-reach test is a good measure of fl exibility of the lower back and backs of the upper legs.