At this time there is also rapid growth and development of the bones
which lengthen rapidly, and are still soft and cartilaginous in places.
It is all-important at this period, therefore, that the muscles on the
two sides of the body receive roughly the same amount of use, otherwise
there is grave danger of some deformity, such as lateral curvature of
the spine, developing.
While the bones are in this condition of rapid development, all
muscle-straining attitudes, such as sitting upright at a desk,
practicing at the piano, writing, painting, etc., should be kept within
such limits as never to entail real fatigue. Young girls at this period,
even more than boys, require all their strength and vitality to support
them in their rapid growth. This does not mean, however, that all
muscular exercises must be forbidden during the period of puberty, which
may be reckoned as from twelve to sixteen in girls, and from thirteen to
sixteen in boys. The point is that violent, really fatiguing exercise,
such as hockey, hunting, cycling tours, mountain climbing, etc., as well
as all occupations which entail the holding of the muscles tense and
fixed in one position for a long period, should be indulged in very
sparingly, if at all. The young girl can obtain all the exercise
necessary for health in less strenuous outdoor pursuits such as golf,
croquet, a little not too strenuous tennis, walking, etc.