Physical fitness is the ability to meet the physical demands of daily life and to resist diseases associated with inactivity. Physical fitness enables people to perform well in sports and other activities, and to look and feel their best.

Physical fitness can be classified into two main kinds: (1) performance-related and (2) health-related. People face different physical demands in the course of their occupations and leisure time. Therefore, the necessary type of conditioning, which may be called performance-related physical fitness, varies from one individual to another. For example, a stockbroker who runs marathon races for recreation requires a high capacity of the heart and lungs to deliver oxygen to leg muscles. On the other hand, a factory worker who lifts heavy crates but reads for relaxation primarily requires great leg and upper body strength to meet daily physical challenges.

The requirements for health-related fitness are similar for all people. Everyone must maintain certain aspects of health-related fitness to feel good and to resist disease.