Asymmetrical movements arc those in which the sagittal planes for the head and trunk do not lie in the sagittal plane of the fundamental position throughout the whole movement, or in which the extremities of both sides do not move in similar and simultaneous movements (e.g., side-bendings, rotations; among these I also include "rollings" of the trunk or head, or of the extremities of one side).

Alternate-sided movements * are those (asymmetrical) movements which arise by moving the trunk or head, or only the extremities, alternately first to one side and then to the other in the sagittal plane in similar (though not simultaneous) movement (examples of such movements we have in walking, in the "ringing" of Swedish gymnastics, in alternate rotations, etc.).

Most systems of gymnastics contain both exercises on the spot and exercises with progression (on the floor or along some apparatus, e.g., the boom). Intermediate forms are to be found. For example, we have such in Frenkel's gymnastics, when the patient rotates on one heel round the long axis of the leg, while with the other leg he takes steps round a narrow circle.

In gymnastics with apparatus or machines, e.g., with Zander's, Krukenberg's, or Herz's apparatus, no progression takes place, for all the exercises are kept on the spot by the apparatus.

Gymnasts use, both in educational and medical gymnastics, a method of gradually increasing the strength of the movements (also called "progression "). By this is really meant an increase in the combined muscle action in the movements, but progression may also include increased functional activity for the other organs of movement. Such progression may be made in various ways. All movements may be made more difficult by increasing their speed or their duration. In resistive movements one may increase the resistance, of whatever kind it may be, by increasing the lever arm by means of which the resistive power (or weight) works; similarly, one can diminish the patient's lever. In certain exercises one can, as may be easily seen, increase the weight of resistance to the exercise by a different position, thus producing a longer leverage for the centre of gravity in the corresponding part of the patient's own body. One may increase the resistance by changing its direction towards the force of gravity. Further, one may progress in gymnastics by making the movement more complicated. Externally the muscle action is increased by taking away the support or diminishing the supporting area, e.g., by changing standing position to toe-standing; in this way one increases the work necessary for both muscles and nerves in balancing. By increasing the strength of the nervous impulses to the antagonists of the muscles used in the movement (in the self-resisted exercises), the work of the muscles and nerves needed for a movement is similarly increased.

* Not to be confused with "change movements." These are made use of in educational gymnastics, and are a series of symmetrical positions and movements following usually in a certain order and in unbroken sequence.

In gymnastics one may limit the muscle action to certain muscles, which is principally done by the form of the movement and by external arrangements which dispense with the action of other muscles. And one may, by fixing other joints by external means, limit the movement to a particular joint. These methods of limiting the functions of muscles and joints to single muscles and joints is called in gymnastics isolating them.

But one hears gymnasts talk about the whole, or the outer or inner part, of the range of movement. The whole range of movement of a muscle is represented by the greatest possible distance between its origin and its insertion, irrespective of the length of the tendons. Biceps brachii, therefore, works in its whole range of movement when it contracts concentrically from full extension to full flexion at the elbow joint. During the movement between half-way and complete flexion it works only in the inner part of its range of movement; during movement between half-flexion and complete extension it works only in the outer part of its range of movement. In concentric "head side-flexion to the left" the scalene muscles on the left work in the inner part of their range of movement; in eccentric head side-flexion to the left the scalene muscles of the right side work in the outer part of their range of movement, etc. Naturally muscles may work freely, actively, concentrically, eccentrically, or statically in any part of their range of movement. By exclusive, especially by concentric work in the inner part of the range of movement lengthened muscles may be shortened; by exclusive, especially by eccentric work in the outer part of the range they may be lengthened. Both aims are attained extremely slowly and require much work (sec later on Contractures).

The Germans have schemes of movements other than the one given above, which was arranged by Ling from ancient models, and which we Swedes have generally adopted. More particularly Herz has given a classification which, by reason of its freedom from rigidity, and its regard to practical considerations, seems to me to offer a sound conception of modern methods to medical gymnasts who are also doctors. Besides simple passive and active movements he distinguishes between resistance movements,* self-resisted movements, movements exercising co-ordination, and rhythmical movements regulated and helped by pendulum or balance-wheel action.

* The resistance movements of Herz are the same as those of Ling's system. Herz calls concentric movements active-duplicated, eccentric movements passive-duplicated, which seems to me less suitable than Ling's nomenclature above referred to.

We shall deal first with the physiological and therapeutic effects of active movements. Afterwards we shall consider what is special to passive movements and positions. Here we shall have the opportunity of considering treatment by assisted and resisted exercises, self-resisted movements, and co-ordination movements, i.e., Frenkel's exercises, so widely adopted since 1870 for treatment of ataxy in tabes.

Here I need therefore only mention the elaborately developed movements regulated by pendulum or balance-wheel action, developed so largely first by the Swedish Dr. Gustaf Zander, and afterwards by Herz, Krukenberg, and others. In these movements the nature of the movement is altered in various ways; the patient goes through every class of Ling's scheme of exercises. When the patient sets going the pendulum or balance-wheel his movement is a concentric resisted movement. After a few minutes, during which the patient neither assists nor resists the movement of the pendulum or balance-wheel, his own movement becomes active without resistance. Afterwards when he follows without resistance and is himself moved by the movement of the pendulum or balance-wheel his own movement becomes passive. During the last part of the movement it becomes an eccentric resistance movement to the extent to which the patient resists the vital force of the pendulum or balance-wheel and is overcome by it.

The movements may be performed without an external special resistance (reine Forderungsbewegungen), or with such resistance (belastete Forderungsbewegungen), but the difference between these is physiologically quite unimportant. The movements so "regulated and helped" are used chiefly in cases of joint stiffness. They are performed by means of rhythmical alternate play of antagonistic muscles, and have, of course, the effect upon the circulation associated with all muscle work, which is fully described below. As in working a "spinning-wheel," which seems to supply a model for the apparatus, they call into play chiefly the lower "sub-cortical" nerve centres and seem to have a soothing influence. For my part I consider that their chief importance lies in the fact that they exercise the joints and their corresponding muscles. For the rest the reader is referred to the study of walking for a more complete interpretation of these movements, which form an important part of Zander's so-called medico-mechanical gymnastics. Walking on level ground may be regarded as the prototype of the "unweighted," hill-climbing as the prototype of the "weighted." rhythmical movements.