CHAPTER XVII MUSCULAR ACTIVITY (Part 3)

Shoulders as a Type of Faulty Carriage. Their Cause. — The carriage of the shoulders well illustrates the closing statement of the last para- graph. Some people have square, while others have sloping, shoulders; in some the shoulders are held back so that the upper portion of the back is approxi- mately flat, while in others they droop forward, thus causing the upper chest to be more or less contracted and the back “round.” To some extent these differ- ences may be due to hereditary structure; but they result, for the most part, from causes which are largely if not entirely under individual control. There is little or no excuse for round shoulders in - healthy people, and the marked effect of training is evident in the fine bearing of well-trained soldiers. The truth of this statement is seen when we consider how the deformity is usually acquired, the chief causes being the following. (a) Faulty Posture. — Round shoul- ders are uncommon among people whose work requires an erect carriage of the body; for example, among those who carry things upon the head. With most, however, the occupations of daily life lead to bending forward over work ; writing, drawing, sewing, lifting, gar- dening, paving, machine and tool work at once occur as examples. The trunk is held in such a position that the shoulders tend to fall forward of their PE wae ee eT ee MUSCULAR ACTIVITY B23 own weight. This tendency is aided by the wrongly curved , backs of most chairs, — which seem as if planned especially O ccipital Bone ~_ Hii pln BA EN Fic. 106. Some of the muscles of the back On the left side are shown those immediately under the skin; by dissecting away this first layer, there are exposed the muscles shown on the right side to force the shoulders forward, —and in boys by the use of many forms of suspenders. (b) Improper Balance in the Play of Antagonistic Muscles. — The position of the shoulders with reference to the ribs, 324 THE HUMAN MECHANISM vertebral column, and breastbone is largely dependent upon the action of several groups of antagonistic muscles, the — most important of which are those of the breast and those of the back. Figures 106 and 107 show the general antag- onistic action of these muscles. The contraction of the great breast (or pectoral) muscle pulls the shoulder for- ward and nearer the breastbone ; the contraction of the back muscles (rhomboideus, trapezius, and others) pulls them backwards and nearer the backbone. Both groups of mus- cles are kept in a state of sustained moderate contraction (or tone) by the nervous system; but if the back muscles relax, while those of the pectoral group remain in tonic contraction, the shoulder will be pulled forward and the back will be round. Obviously the maintenance by the nervous system of the proper balance in the action of these and other antagonistic groups of muscles is essential to correct carriage of the shoulder. (c) Deficient Use of the Back Muscles, with or without the Excessive Use of the Breast Muscles.— Most occupations and activities involve greater use of the breast muscles than of the back muscles. Striking a blow with a bat or an ax, throwing a ball, and similar actions are ALG more usual than acts, like SS pi pulling taffy, which extend SS; the arms and draw the Fic. 107. The skeleton of the trunk shoulder blades closer to- seen from above. After Demeny gether. Movements of Showing the antagonistic play upon the the first kind obviously apes oF Pee ten of the breast strengthen the breast and ‘stretch the back muscles ; those of the second kind have the opposite effect. Conse- quently any marked preponderance of pectoral action tends om ACY hes MUSCULAR ACTIVITY O25 to elongate the back muscles; and unless this is counter- acted by movements of the opposite character, which stretch the breast muscle, the pectoral and back groups become “set,” as we may express it, in improper relative lengths. Fic. 108. Correct and incorrect positions of the shoulder girdle. After Demeny The result is round shoulders. Consequently one of the most important things to have in view in gymnastic work is the use of movements which train the back muscles and stretch the pectorals, thus counteracting the effect of the one-sided use of these two groups of muscles in ordinary occupations. 14. The Period of Growth Especially Favorable for the Acquisition of Round Shoulders and Other Deformities. — The length of a growing muscle is determined largely by the distance between its origin and insertion! during the period of growth. The breast muscle will grow to be a longer muscle when the shoulders are held back by the back muscles than when they are habitually allowed to droop forward. In the former case the pectorals grow to sufficient length and do not tend to pull the shoulders forward and downward ; and we avoid the excessive length of the back muscles, which makes it necessary for them to take up their own slack before they can keep the shoulders in position. 1 Where a muscle is attached by its two tendons, the point of attach- ment against which it usually pulls or is fixed is known as its origin, while the one it usually moves is known as its insertion. Thus the origin of the pectoral muscle is the breastbone and ribs, its insertion the shoulder and the upper arm, 326 THE HUMAN MECHANISM The student can now appreciate the fact that it is in youth, during the period of growth, that deformities are most readily acquired and most easily corrected; for the muscles, the ligaments, the bones, are then in their forma- tive stage. In the case in point, if the boy or girl holds the shoulders properly, the pectoral and back muscles of each side adjust themselves to their proper length; and the shoulders grow into the correct form, just as the sapling which is not bent nor deprived of proper sunlight grows into the symmetrical,: beautiful tree. During the period of growth, then, —say up to at least the twentieth year, — we can hope to accomplish most in correcting and especially in preventing deformities. The correction and prevention of round shoulders evidently depends upon the proper training and use of the muscles which play upon the shoulder; it is therefore a legitimate part of gymnastic training, for gymnastic training is largely the art of learn- | ing to use the muscles properly. Where there is a special defect to remedy or prevent, special exercises are required. These are of the general character of the “setting-up” drill of the soldier, and in the case in point we accomplish our purpose by using movements which in the first place stretch the pectorals and even overextend them; in the second place, give to the back muscles the exercise which they fail to get in our ordinary occupations, and so bring up their strength, their ability to withstand fatigue and to maintain the tonic contraction demanded of them; and which, in the third: place, give us the knowledge of the correct position of the shoulders. 15. Education of the Consciousness of Correct Posture. — In explanation of the last point we may say that when one habitually carries the shoulders properly he feels that he is taking an awkward position when he allows the shoulders to droop; on the other hand, the man who MUSCULAR ACTIVITY BVA habitually allows the shoulders to droop forward feels that he is in an unnatural position when he holds his shoulders back. This is largely because in the first case the back muscles and in the second the pectorals must be put on a stretch ; it is also due to the fact that the sensations derived from the habitual posture, whether it be correct or incorrect, have impressed themselves on consciousness as signs of the normal conditions ; to take any other posi- tion is to experience the feeling of something unusual or abnormal. We learn of the position of parts of our body with reference to one another by sensations derived from the muscles, tendons, joints, etc. (see Chapter XIV, p. 262); and the sensations of position which result when we assume the habitual posture fix themselves in our thought as signs of the normal posture. Our practical, working idea of normal posture, indeed, is nothing more nor less. than our experience of the sensations of position resulting from habitual posture. The man who never carries his shoulders back really knows nothing of their correct posi- tion, because the sensations from correct posture are lack- ing; he knows no more about them than a man blind from his birth knows of the color of a landscape. One of the first steps in correcting this and similar faults must be to experience the muscular sensations which come from cor- rect carriage ; and the more frequently these sensations are experienced, the better does the subject become acquainted with them, the more likely are they to replace his erro- neous judgment. It is only through the sense of position that we can hope to acquire the practical working knowledge of correct carriage. What we learn by reading about the matter or by looking at pictures or statues of the correct figure is of little use ; for such ideas come to us only through the eye, and we obviously cannot depend on our sense of vision HS 828 THE HUMAN MECHANISM to inform us whether we are carrying ourselves properly or not. We do not “see ourselves as others see us”; gen- erally we do not “see ourselves” at all. It is only the sense of position that is capable of reminding us the instant we go wrong; and this sense can be trained properly only by actually assuming the correct posture. 16. The More Important Faults of Form and Carriage. — We may now pass to the consideration of the more important deformities, which it is the aim of special mus- cular exercises to prevent or correct. (a) The failure to hold the neck erect (allowing it to bend forward). — This results naturally from the fact that the weight of the head will do this, pro- vided the tendency is not corrected by the proper training of the muscles _of the back of the neck and trunk. The position of the head usually another cause of this bad habit. (6) Round or stoop shoulders. — These defects have already been suf- ficiently dwelt upon (p. 322). (c) Too great backward (dorsal) PO eee convewity of the spine in the thoracic proper (1) and improper 7€gton, and too great forward (ventral) (2) carriage of the ver- convexity of the spine in the abdominal oem tee Atter region. — A certain amount of such curvature is normal in these regions (see Chapter IT); but there is usually a tendency to exces- sive curvature because of the weight of the parts of the body which the spine must support. Every one knows that it is an effort to sit erect ; and this feeling of effort comes from the fact that the spine is straightened, or rather its curvature kept normal, by the action of a rather com- plicated group of muscles, — the erectors of the spine. To taken in reading, sewing, etc., is a SSeS OS FP Pee ey ye jp if A» MUSCULAR ACTIVITY 329 sit, or stand, or walk erect involves the activity of these muscles ; when they cease to act the faulty curvature be- comes more pronounced. Hence the value of all exercises which tend to straighten the spine, — exercises, for exam- ple, in which, while standing on the feet, we try by our own muscular effort to make ourselves as tall as possible. They train and strengthen the muscles in question ; they stretch their antagonists, just as throwing the shoulders back stretches the pectorals; and they impart to us by actual experience the sensation of being erect. (d) Lateral curvature of the spine. — When the spinal column and its attached ligaments and muscles are prop- erly developed there is little or no lateral curvature of the spine; the two halves of the body are symmetrical with regard to the median plane of the body, although a con- siderable amount of bending of the spine as a whole to one side or the other is possible. It is, however, quite possible, by maintaining incorrect positions, to acquire a more or less pronounced lateral curvature in which the muscles and ligaments of the concave side become short- ened and those of the convex side lengthened. Perhaps nothing is so responsible for all these faults of curvature of the spinal column as improper positions at the school desk, and much can be done to prevent them by properly constructed school furniture and careful attention to cor- rect position. But it is not wise to depend on these alone. No desk ltas been constructed in which correct posture can be indefinitely maintained with ease, and we have still in any case to contend with the force of gravity. Active exercises which straighten the spine should supplement the other measures. Experience has well established the fact that the true preventive and remedy lies in move- ments which elongate the spine. (e) We have elsewhere (p. 172) pointed out the im- portant action of the muscles of the abdominal wall in Da0 THE HUMAN MECHANISM supporting the abdominal viscera, especially those, like the stomach, the spleen, and the intestine, which are sus- pended from the dorsal wall of the abdominal cavity. Fig. 187 will at once make clear how the relaxation or elongation of the abdominal muscles, by removing support from these viscera, permits their weight to pull unduly upon the mesentery, and so to stretch this support. It is also not improbable that the tense mesentery at times, by pressing upon thin-walled veins and lymphatics, interferes with the circulation of blood and the flow of lymph in some organs, and so leads to trouble. A pot-belly is not. a thing of beauty, and there is every reason for thinking it to be undesirable from the hygienic point of view. It is prevented, in the first place, by every movement which prevents undue lumbar curvature of the spine, and, in the second place, by exercises of the abdominal muscles, which result in their improved tone. These, however, like all - corrective exercises, must be followed up by maintenance of the correct position of the trunk. 17. Special Exercise for the Training of Nervous Coordi- nation. — A man or woman may possess none of the de- formities noticed above, — the anatomical form of the body may conform to the best ideals, —and yet the positions and movements of the body may be awkward, inexpert, ungraceful. In other words, the muscles may be well devel- oped but the individual may be deficient in the power of easily codrdinating their action in the accomplishment of desired ends. After what hag been learned of the part which the nervous system plays in directing our actions, the brevity of any reference to this purpose of physical training will not mislead the student into thinking that it is of little importance. We have learned that the maitite- nance of equilibrium, when the body is at rest and when it is in motion, and the execution of complicated move- ments, both require training of the nervous system by use. a ce oo Teepe eet needs a jibe seis ee sta th of ibe? 6 bid bil eked Ce dae MUSCULAR ACTIVITY dal The range of activities for which we can train is very exten- sive ; playing upon musical instruments, the execution of gymnastic feats on the parallel and horizontal bars, the traveling rings, or the trapeze, are only a few examples of what can be done by the training of the nervous system by practice. A large part of gymnasium work consists in this sort of training, and there is almost no limit to the forms of exer- cise to which we may train, — vaulting, jumping, balan cing the body on one foot while various movements are made, the tricks of the parallel and horizontal bars, trapeze, etc. Is there any principle to guide us in the choice of what we shall do? In reply to this question we may say that the leading principle should undoubtedly be that of training for what will be useful, and while we need not discard all training which cannot be justified on this ground, that which is useful should not be sacrificed to that which is not useful. A large amount of skill is required to walk upon the hands with the feet in the air, and the thing can be done very gracefully by training ; but it is certainly better to cultivate the habit of walking gracefully upon the feet. And yet one may see profes- sional gymnasts who are extremely graceful while perform- ing their tricks, but whose gait is clumsy and awkward. 18. Balance Exercises. — It is evident that by far the greater number of our customary codrdinated movements are made on the feet. Hence the value of so-called balance exercises in the widest sense, whether they consist in the execution of difficult movements while standing on one foot or on the “ walking beam,” or in making a proper landing from a jump ora vault; all of them afford training of those reflexes by which we retain control of the body in motion, thus securing grace of posture and carriage. The general purpose of training these reflexes is the same as the purpose of those exercises which correct 332 THE HUMAN MECHANISM deformities; they do for the nervous mechanism of the movement what the others do for the skeletal parts and