The exercises selected must be such as will strengthen these particular groups of muscles, and, while taking the exercises, the entire attention must be concentrated on the part being exercised.
Any lack of symmetry in the chest, spinal curvature, or actual weakness of the lungs will necessitate the prescribing of special and carefully selected exercises.
As to the exercises themselves, they should be so arranged as to bring into play in a methodic manner all the muscles. All special and corrective work must be supplemented by general work, which will increase the organic vigor of the heart, lungs, and chest necessary to meet the vital demands of the whole system. Games are, of course, most useful for this purpose, but the games should not be too violent.
In most free exercises the limbs are used for weights of resistance. In a man weighing one hundred and fifty pounds the arms usually weigh about ten pounds each and the legs twenty pounds.
The Causes of Round Shoulders.—The general conditions are those that produce muscular or constitutional weakness, as rapid growth, overwork, the impure air of ill-ventilated rooms, acute illness, near-sightedness uncorrected by glasses, lack of proper exercise, and the wearing of clothing supported by suspenders bearing on the points of the shoulders, tending to pull them downward and forward, or even to produce a painful deformity of the scapula.
It is the rule rather than the exception to find, with round shoulders, some inequality in the height. The right shoulder is apt to be the lower, owing to the carrying of burdens on the right arm. Habitual standing with the weight on the right leg contributes to a good many cases. Games in which the right arm is almost exclusively used is another cause.
Fig. 29.—The spinal column (Church and Peterson).
The Causes of Spinal Curvature.—The spinal column forms the central support of the body, and, for grace and suppleness of motion, its thirty-four joints should be constantly exercised, as well as the muscles which hold it erect and support the head upon it, as well as attach the shoulders, hips, and legs more or less closely to it. In brief, all the muscles of the back need varied and regular exercise to maintain the erect position of the body, and from early childhood especial attention should be given to develop and strengthen this region of the body.
The normal movements of the spinal column are flexion, extension, side bending, and torsion. Flexion and extension take place, for the most part, in the lumbar and cervical regions.