When we come to consider the muscle training of each particular muscle or muscle group, much space will be saved if we realise at once that the training of one muscle is merely the reverse of the process involved in training its antagonist. Hence much repetition of detail can be avoided. Also, it is no less impossible to describe a process of re-education than to teach the manipulations of massage by written word alone. These things must be demonstrated to be taught properly. All I can do here, therefore, is to indicate the postural element of the training, and this can again be compressed into smaller compass if we once realise that the posture to be assumed in the earliest stages of muscle training is, as a rule, identical with that in which pure relaxed movement is administered. (See Chapters VII. and VIII.)

In the earliest stage in training abduction of the shoulder the patient is recumbent and the whole of the upper extremity rests on a smooth couch. If the patient is still wearing an abduction splint, the arm must not be allowed to approach the trunk nearer than a position of 45°. The patient is taught to try to abduct a few degrees, then to rest, then to try to gain a few further degrees. Then he is taught to move the limb to and fro on the horizontal plane. As soon as he can do this the trunk is elevated a few degrees by the insertion of a pillow; and, as recovery progresses, the elevation of the trunk increases till an angle of 45° is reached. The remaining stages are more easily passed through if the legs from the knees downwards are allowed to hang over the end of the couch. It must be remembered that the final degrees of abduction can only be performed in the horizontal plane when the internal epicondyle points directly forward. This is not the best position in which to practise the earlier stages of abduction. In the ordinary mid-position of rotation a limit to abduction is reached when some 30° more movement still remain, and at this point the arm is carried slightly forwards with a sort of semi-circular sweep to aid rotation, and is allowed to drop backwards by the side of the head. The alternative training by the weight and pulley is first to abduct the arm by means of weights attached to the overhead pulley. As these are reduced, effort is called for to perform the abduction which has hitherto been performed by the weights. When the last weight is removed the patient is ready to perform "free" abduction against gravity. The next stage is to grasp the handle attached to the rope that passes round the floor pulley and abduct again. As the weight is increased, the work now increases in proportion (see Figs. 58 and 59, pp. 111 and 113).

The movement of abduction of the arm is very complicated. The deltoid (and supraspinatus according to MacKenzie) abduct the arm to nearly a right angle at the gleno-humeral joint. Further abduction takes place by movement at the sterno-clavicular joint and is performed chiefly by the trapezius, aided by the levator anguli scapulae. The serratus magnus probably also actually aids rotation of the scapula, but this is not its main function, which is to maintain the contact of the anterior surface of the scapula with the chest wall. Deltoid training should begin at some 70° of abduction to 85°, that of the scapula muscles at 165° to 180°. The two processes can be carried on simultaneously. If the serratus only is weak a cuff and collar rest (see Fig. 76, p. 150) will be all that is required. Although synergists in one sense, that of generally assisting abduction, the serratus magnus and trapezius are antagonists in so far as the former tends to pull the scapula downwards and forwards, while the latter pulls it inwards and upwards. The rhomboids draw the scapula inwards and slightly upwards.

The training of the antagonist, the pectoralis major, can only be advanced without the aid of apparatus from the sitting position to the recumbent. To pass further would involve the use of the Trendelenberg position. Thus training with the weight and pulley is preferable when this stage is reached. It is well to remember that the use of the weight and pulley while the patient is recumbent is a most valuable combination of treatment in these, and in many other, instances of muscle training. Doubtless the latissimus dorsi and the scapulohumeral muscles, except supraspinatus, can act as synergist adductors.

It is not easy to rest a deltoid without the aid of an abduction splint, but most of the strain can be taken off the muscle by use of a sling applied as for fracture of the clavicle (see Fig. 77, p. 151), and a considerable degree of tension can be relieved by resting the hand in the side pocket of a jacket or even in the trouser pocket, by carrying it between the higher buttons of a waistcoat or supported on a simple loop of bandage from the opposite shoulder. The forearm should be flexed to 45°. The adductors of the shoulder are in the rest position in the upright attitude.

The training of the rotators of the shoulder (MacKenzie describes the infraspinatus and teres minor as external rotators, and the latissimus dorsi and subscapularis as internal rotators) should be performed in the first stages prone for the internal, and supine for the external rotators. In the upright position they are free to act in the "zero" position. MacKenzie regards the great pectoral as an adductor only and not as a rotator, and this gives the clue to training. It is, from this point of view, best to regard it as a primary adductor and synergist rotator. The rotators of the shoulder are at rest while the limb hangs at the side, the forearm in mid pronation and the thumb facing directly forwards. If the forearm rests on a sling, while the external epicondyle of the humerus faces directly forwards, the internal rotators are relaxed, the external are in tension.

Flexion and extension of the shoulder should, in the early stages at least, be considered to be the function of the coraco-brachialis and (according to MacKenzie) the teres major respectively. It is wise to regard all the three portions of the deltoid as acting in unison (as the great abductor of the shoulder only, i.e., of the gleno-humeral joint) throughout the earlier stages of training. Flexion and extension of the shoulder should be performed with the arm and forearm resting on a smooth board. In the horizontal plane the action of gravity is zero, as the board is dropped towards the patient's side, movement towards the middle is assisted by gravity, and that away from it is resisted. Depression of the support is continued until the maximum of work is done in the vertical position by one muscle when raising the arm forwards, by the other when raising it backwards. Movement towards the vertical gives assistance from gravity to the muscle that performs the movement. The muscles, of course, are at perfect rest while the limb hangs loosely at the side.