The strength, Flexibility and endurance of the body can be increased through regular exercise. Such improvements are primarily localized in the muscles and organs which are exercised – one cannot strengthen the arms and shoulders by exercising the legs.
To improve the condition of all muscles one must undertake a program which will provide them all with work. The strength of a muscle is measured by the amount of force that, that muscle can exert and is dependent upon the size and number of muscle fibers that can be brought into action at any one time and the frequency of the nerve impulses to them. Endurance is concerned with the ability to repeat an action over and over again, or to sustain a muscular contraction. Since the fuel for muscular contraction is carried in the blood, endurance is chiefly dependent upon the functioning of the cardio respiratory system, (heart, blood vessels, and lungs – that is, the ability of the body to transport food and oxygen to the muscles, and waste products away from them, efficiently.
The human body requires proper use to function efficiently and endure. The body is very different from a machine that wears out with use. Most persons have noted how the muscles of an arm or a leg in a cast become smaller and weaker the longer the arm or leg remains so encased. While this is a dramatic example it is in effect what happens to the muscles of the body in a milder way when these muscles are not used enough. Exercise over and above the normal demands of daily living is essential to the development of an efficient, strong, and durable body.
The resultant more pleasing appearance and sense of well-being are added benefits that cannot be overlooked.
Caution – before you start
If you have any doubt as to your capability to undertake this program, see your medical adviser. You should not perform fast, vigorous, or highly competitive physical activity without gradually developing, and continuously maintaining, an adequate level of physical fitness, particularly it you are over the age of 30.