In most early cases the faulty attitudes are clearly the result of muscular weakness.  The growth in size has not been accompanied by a corresponding development of the muscles.  This condition is most frequently met with in rapidly growing girls, and it is one of the most common causes of lateral curvature.  In these cases proper gymnastics are indicated, but they should be prescribed and carried out with much care.

It is upon the erectness, suppleness, and strength of the spinal column that most of the power and grace of the body depend.

Lack of ventilation is a fertile cause of headache, anemia (or an impoverished condition of the blood in iron and oxygen), and dyspepsia.  All these are rare before but common after twelve years of age.

Exercise.—­ In physical culture the object aimed at should be the symmetrical development of all the muscles of the body.  Hence the necessity for bringing every individual muscle into play, at first for its development, and later for its maintenance.

The tendency of almost all forms of exercise is to develop some portion of the body at the expense of the rest.  The most perfect form of exercise is therefore that one which will most nearly call into play all the muscles of the body.

Walking.—­ Walking is the only form of exercise which may be said to be universal.  In walking the muscles of the chest get little exercise, and those of the spine and abdomen even less.  In walking the arms should swing easily at the sides, both from a physiological and an esthetic point of view.  If the girl is weak or is unaccustomed to take any exercise, the guide for the amount of exercise taken at any one time must be this:  At the first sense of fatigue, stop at once and rest, otherwise positive harm instead of good may be accomplished.  The girl who depends on walking for her outdoor exercise should walk at least three miles every day, and walk at the rate of three miles an hour.

After acquiring as great a walking speed as is consistent with a graceful and easy carriage, the running exercise should be begun, gradually increasing the distance, but not the rate of speed.

In exercising, all tight clothing about the neck, chest, and waist must be removed.  Pure air and full breathing are required during and after exercise.  Full breathing not only promotes the change of air in the lungs, but also quickens the functions of the circulation and digestion.  Eating must be avoided shortly before or shortly after any considerable exercise, as it impairs digestion.

Running.—­ Running is the best exercise for developing the breathing capacity.  While brisk walking is allowable, fast running is not.  The rule for running is to begin slowly, run moderately for perhaps fifty feet, then increase the speed gradually; but in running for exercise, never speed to the utmost.  A five-mile gait is quite sufficient.  The run should be closed with the same moderation with which it was begun, and the girl should never stop short, as this sudden arrest of action gives a most undesirable shock to the heart.