How fit should you be?
Heredity and health determine the top limits to which your physical capacity can be developed. This is known as your potential physical capacity. This potential capacity varies from individual to individual. Most of us for example, could train for a lifetime and never come close to running a four minute mile simply because we weren't "built" for it.
The top level at which you can perform physically right now is called your "acquired capacity" because it has been acquired or developed through physical activity in your daily routines.
Your body, like a car, functions most efficiently well below its acquired capacity.
A car, for example, driven at its top speed of, say, 110 miles per hour uses more gas per mile than when it is driven around 50-60 miles per hour, which is well below its capacity. Your body functions in the same way, in that the ratio of work performed to energy expended is better when it functions well below acquired capacity.
You can avoid wastage of energy by acquiring a level of physical capacity well above the level required to perform your normal daily tasks. This can be accomplished by supplementing your daily physical activity with a balanced exercise programme performed regularly. Your capacity increases as you progressively increase the load on your muscular and organic systems.
Exercise will increase physical endurance and stamina thus providing a greater reserve of energy for leisure time activities.