From a gymnastic point of view movements are divided into Active and Passive.

By active movements we mean those in which the patient's muscles are innervated and brought into action.

By passive movements we mean those performed in the patient's joints by some outside force, his muscles not being used.

Active movements are divided into -

1. Free movements, performed by the patient himself without the assistance of the operator, e.g., Standing 2 (double) Arm-raising-outward and-upward.

2. Resistance movements, performed with the help of an active operator.

Resistance movements are divided into -

(a) Concentric.

(b) Eccentric.

A third form of active muscle action may here be described, though it is not connected with any definite movement, viz., the so-called Holdings. By this is meant that the patient holds himself in a certain position already taken. For this certain definite muscles are brought into action, but do not become either longer or shorter while working, and consequently do not perform any actual mechanical work, though they are innervated and brought into action; e.g., Leg-forward-lying Holding, when the patient for a short time maintains himself in Leg-forward-lying position.

In concentric movement both ends of the working muscles are brought nearer to their respective centres and the muscles become shorter. This is the case when a movement, e.g., flexion of the elbow joint, is performed by the patient against the resistance of the operator or some other outside force (flexors work concentrically).

In eccentric movements the muscles become longer while working, i.e., their extremities go further from their centres. This takes place when a movement, e.g., extension of the flexed elbow, is performed by the operator or other outside force, while the patient resists the movement (flexors work eccentrically).

N.B. - Even in free movements the muscles work concentrically or eccentrically, or both, but the resistance is caused by the weight of the moved part of the body and so cannot be modified.

In holdings the length of the muscles remains unchanged, so that no movement is performed, but the muscles are innervated, oxidation processes in them are increased, and they are brought into action.

The value of resistance movements lies in the fact that they can be modified and so perfectly adapted to the strength of the patient.

Concentric movements require a large amount of elastic force, and of the heat given off by combustion in the muscle only about 25 per cent. is converted into useful work; the rest goes to raise the temperature of the muscles and of the body. This is the form of movement most used.

Eccentric movements are less tiring, and of the heat given off about 90 per cent. is transformed into work. These movements are used specially in the treatment of paralyses, because muscles are able to perform eccentric movement long before concentric. They are also used in treatment of diseases which are associated with disturbances of innervation, e.g., in chorea and occupation neuroses, because they compel the patient's careful attention to the innervation of the working muscles. Often the combined concentric and eccentric forms are used, e.g., in the ordinary High-ride-sitting Alternate Trunk-rotation.

In "holdings" combustion is considerably less rapid than in either of the other kinds of muscle action, and no part of the heat given off is converted into mechanical work. Holdings are specially used in the treatment of spinal curvatures. Their chief value lies in the fact that they educate the patient's sense of the correct innervation of the muscles in a particular position, but they also exercise the muscles, and in certain cases stretch the contracted soft parts - e.g., in Side-lying Holding.

Besides the gymnastic division of movements into active and passive, from a physiological point of view we may divide them into two groups, Voluntary and Involuntary.

Voluntary movements are those which are performed as the result of conscious and controlled impulses of the will.

Involuntary movements are those brought about by impulses which are not directly under the influence of the will. The most important of these are : associated movements, reflex movements, and peristaltic movements of the intestines, as well as the cardiac movements.

By associated movement is meant a movement arising involuntarily at the same time as another (usually voluntary) movement. There are several different kinds.

(a) Associated action between certain non-striated and striated muscles, e.g., between the muscles of the iris and the external striated muscles of the eye (contraction of the pupil when the optic axes are made to converge).

A similar associated movement exists between the non-striated muscles of the alimentary canal and the external abdominal muscles.

(b) Associated movement, or a tendency to it, between the muscles of the two halves of the body.

(c) Associated movement between muscles which do not apparently stand in any close connection with one another, e.g., grimacing when performing movements of precision, the tendency to flex the hip joint in heaving movements, or to hold the breath during strong movements even when the working muscles do not arise from the chest.

By a reflex movement is understood a movement which arises involuntarily as the result of a stimulus affecting a sensory nerve being transferred to a motor nerve, and thus causing a muscular contraction.