Medical Gymnastics is a therapeutic treatment by systematic exercise of the organs forming the motor apparatus of the body.* These, again, consist of the skeletal muscles, which by their contractions convert the chemically stored energy into that of movement or position; of the bones, which act as levers for these movements; of the joints, in which the movements take place round definite axes; of the centrifugal motor nerve-elements, from which the motor impulses arise and are conducted; and of the centripetal sensory nerve elements, upon which also the form and steadiness of the movement depend. The physiological and therapeutic effects of medical gymnastics in the first place, of course, concern these organs, but through them affect the remaining parts of the organism, so that one can justly say that no organ remains unaffected by them. Medical gymnastics is used moreover in many cases for its therapeutic effect on organs other than those of the motor apparatus.

The motor apparatus may be exercised by taking up certain definite positions +; the muscle work required for this purpose is called static muscle work.

The positions of Swedish gymnastics were arranged and classified by our famous countryman P. H. Ling. His starting positions consist of fundamental positions and derived positions. There arc five of Ling's fundamental positions, and a large number of derived positions. (See Arvcdson's description in Chap. IX.)

But the motor apparatus is exercised also, and principally, by movements. Work which performs movement is called dynamic or motor work.

We have to thank Ling, not only for the introduction and arrangement of the positions of Swedish gymnastics, but also for most of the exercises and their various classifications. The most general and usually adopted and widespread of these classifications was taken by Ling from an ancient model. Since Ling's time the exercises have also been classified in other ways, especially by German doctors and authors. As the most important of these Swedish and German classifications promote a clearer insight into both the general technique and the physiological and therapeutic effects of gymnastics, I give them here.

* The motor organs are often exercised for other than purely therapeutic reasons. Healthy persons often take hygienic or dietetic gymnastics, if their daily life without it does not supply the bodily movement so necessary for health. For these and other (preparatory) aims educational gymnastics are used in our schools. We also give our officers and men in the Army and Navy military gymnastics to increase their working efficiency.

+ The Swedish gymnasts distinguish between "positions" and "holdings." By a "position" they mean a position of the body which prepares for certain movements; by "holding," a bodily position which (for its own therapeutic value) is maintained unchanged.

The classification of Ling's Swedish gymnastics is as follows : double, duplicated, resistance concentric ( = shortening).

Movements passive. active.

free (without special support). controlled (with special support).

eccentric (== lengthening).

Passive movements are such as are performed in the patient's joints by some outside force, represented by a person (gymnast), a weight, or a machine. By passive movements it is the joints chiefly that are exercised.

If the passive movements are given by a person he is said to be the "giver of the movement," while the patient is said to "take the movement." (In resistance exercises also we distinguish between the "giver" (gymnast) and the "taker" (patient) of the movement.)

For a movement to be considered as belonging to gymnastics, especially medical gymnastics, it is not necessary that it should take place by the patient's own innervation, as passive movements are also included in medical gymnastics. I am not certain (sec below) that even in passive movements the patient does not often innervate the muscles which are becoming shorter. But there is no doubt that such movements can take place without any innervation. On the other hand, it must be remembered that gymnastics comprises only those movements which take place in the joints of the individual taking the exercise. To include those movements which take place in the joints of the operator would be-as absurd as to include massage manipulations as passive gymnastic movements.

Gymnastics in its usual meaning apparently consists only of voluntary movements. Only the striated skeletal muscles can therefore correctly be said to be "exercised," since they alone can be said, apart from their power to produce involuntary reflex contractions, to contract under the influence of the will, which is transmitted from the ganglion cells in the cortex of the brain to the muscles by means of the nerve-end plates in the latter. Cardiac muscle fibres are, however, striated, but are not under the power of the will; the manner of indirectly exercising these by bodily movements I will return to later on. The striated character of both cardiac and skeletal muscles is doubtless connected with the speed and strength of muscular contraction, and represents a high degree of contractility. The non-striated muscles in the alimentary canal, in the arteries and veins, in the uterus, etc., have slow, comparatively weak, often rhythmic contraction, are not under the control of the will, and cannot, therefore, actually be "exercised."

The characteristic movements of gymnastics are those movements which take place under the innervation of the patient's own muscles, i.e., active movements. If these are performed by the patient without external help or support they are called free movements.

All movements which are performed with the support of some external object or apparatus are said to be controlled by this apparatus.*

But active movements may also be performed with the cooperation of outside forces, represented by a gymnast giving the movement, by a machine or weight, and are then called resistance movements.+