FITNESS for effective living has many interdependent components involving intellectual and emotional, as well as physical, factors. These differ in relative importance from one period of life to another, depending on varying individual roles and responsibilities. But in every part of life, each of these factors is significant.
Fitness rests first of all upon a solid foundation of good health. Be it in the home, on the farm, at the office, in the factory, or in military service—fitness for effective living implies freedom from disease; enough strength, agility, endurance, and skill to meet the demands of daily living; sufficient reserves to withstand ordinary stresses without causing harmful strain; and mental development and emotional adjustment appropriate to the maturity of the individual.
Fitness does not come in a "have" or "not have" package. The level of fitness attained is a resultant of ability to cope with the varied and interacting
Exercise and Fitness. JAMA. 1964;188(5):433–436. doi:10.1001/jama.1964.03060310033007