Physical fitness is used in two close meanings: general fitness (a state of health and well-being) and specific fitness (a task-oriented definition based on the ability to perform specific aspects of sports or occupations).

Physical fitness is the capacity of the heart, blood vessels, lungs, and muscles to function at optimum efficiency. In previous years, fitness was defined as the capacity to carry out the day�_Ts activities without undue fatigue. Automation, increased leisure time, and changes in lifestyles following the industrial revolution meant this criterion was no longer sufficient. Optimum efficiency is the key. Physical fitness is now defined as the body�_Ts ability to function efficiently and effectively in work and leisure activities, to be healthy, to resist hypokinetic diseases, and to meet emergency situations.

Physical fitness is the result of regular exercise, proper diet and nutrition, and proper rest for physical recovery within the parameters allowed by the genome.

Accuracy

Agility

Balance

Body composition

Cardiovascular endurance

Coordination

Flexibility and joint range of motion

Power

Speed

Stamina

Strength

Many sources also cite mental and emotional health as an important part of overall fitness. This is often presented in textbooks as a triangle made up of three sub-sections which represent physical, emotional, and mental fitness. Hence, one may be physically fit but may still suffer from a mental illness or have emotional problems. The "ideal triangle" is balanced in all areas. Physical fitness can also prevent or treat many chronic health conditions brought on by unhealthy lifestyle or aging.

Specific or task-oriented fitness is a person's ability to perform in a specific activity with a reasonable efficiency, for example, sports or military service. Specific training prepares athletes to perform well in their sports.

Fire fighters and police officers must undergo regular Fitness testing to determine if they are capable of the physically demanding tasks required for the job before they are employed. In the Scouting programs of some countries, students can earn fitness badges, such as the Physical Fitness Badge which is earned in the United States.