A Practical Physiology Part 9

Lower Limbs.

Gluteus maximus. adducts the thigh.

Adductors of thigh. draw the leg inwards.

Sartorius. crosses the legs.

Rectus femoris. flexes the thigh.

Vastus externus. extensor of leg.

Vastus internus. extensor of leg upon thigh.

Biceps femoris. flexes leg upon thigh.

Gracilis. flexes the leg and adducts thigh.

Tibialis anticus. draws up inner border of foot.

Peroneus longus. raises outer edge of foot, Gastrocnemius. keep the body erect, and Soleus. aid in walking and running.

Chapter IV.

Physical Exercise.

80. Importance of Bodily Exercise. Nothing is so essential to success in life as sound physical health. It enables us to work with energy and comfort, and better to endure unusual physical and mental strains. While others suffer the penalties of feebleness, a lower standard of functional activities, and premature decay, the fortunate possessor of a sound mind in a sound body is better prepared, with proper application, to endure the hards.h.i.+ps and win the triumphs of life[13].

This element of physical capacity is as necessary to a useful and energetic life, as are mental endowment and intellectual acquirement.

Instinct impels us to seek health and pleasure in muscular exercise. A healthy and vigorous child is never still except during sleep. The restless limbs and muscles of school children pent up for several hours, feel the need of movement, as a hungry man craves food. This natural desire for exercise, although too often overlooked, is really one of the necessities of life. One must be in ill health or of an imperfect nature, when he ceases to feel this impulse. Indeed, motion within proper bounds is essential to the full development and perfect maintenance of the bodily health. Unlike other machines, the human body becomes within reasonable limits, stronger and more capable the more it is used.

As our tenure of life at best is short, it is our duty to strive to live as free as possible from bodily ills. It is, therefore, of paramount importance to rightly exercise every part of the body, and this without undue effort or injurious strain.

Strictly speaking, physical exercise refers to the functional activity of each and every tissue, and properly includes the regulation of the functions and movements of the entire body. The word exercise, however, is used usually in a narrower sense as applied to those movements that are effected by the contraction of the voluntary muscles.

Brief reference will be made in this chapter only to such natural and systematic physical training as should enter into the life of every healthy person.

81. Muscular Activity. The body, as we have learned, is built up of certain elementary tissues which are combined to make bones, muscles, nerves, and other structures. The tissues, in turn, are made up of countless minute cells, each of which has its birth, lives its brief moment to do its work in the animal economy, is separated from the tissue of which it was a part, and is in due time eliminated by the organs of excretion,--the lungs, the skin, or the kidneys. Thus there is a continuous process of growth, of decay, and removal, among the individual cells of each tissue.

[NOTE. The Incessant Changes in Muscular Tissue. "In every tiny block of muscle there is a part which is really alive, there are parts which are becoming alive, there are parts which have been alive, and are now dying or dead; there is an upward rush from the lifeless to the living, a downward rush from the living to the dead. This is always going on, whether the muscle be quiet and at rest, or whether it be active and moving,--some of the capital of living material is being spent, changed into dead waste; some of the new food is always being raised into living capital. But when the muscle is called upon to do work, when it is put into movement, the expenditure is quickened, there is a run upon the living capital, the greater, the more urgent the call for action."--Professor Michael Foster.]

These ceaseless processes are greatly modified by the activity of the bodily functions. Every movement of a muscle, for instance, involves change in its component cells. And since the loss of every atom of the body is in direct relation to its activity, a second process is necessary to repair this constant waste; else the body would rapidly diminish in size and strength, and life itself would soon end. This process of repair is accomplished, as we shall learn in Chapters VI. and VII., by the organs of nutrition, which convert the food into blood.

[Ill.u.s.tration: Fig. 39.--Showing how the Muscles of the Back may be developed by a Moderate Amount of Dumb-Bell Exercise at Home. (From a photograph.)]

82. Effect of Exercise upon the Muscles. Systematic exercise influences the growth and structure of the muscles of the body in a manner somewhat remarkable. Muscular exercise makes muscular tissue; from the lack of it, muscles become soft and wasted. Muscles properly exercised not only increase in size, both as a whole and in their individual structure, but are better enabled to get rid of material which tends to hamper their movements. Thus muscular exercise helps to remove any needless acc.u.mulation of fat, as well as useless waste matters, which may exist in the tissues. As fat forms no permanent structural part of the organism, its removal is, within limits, effected with no inconvenience.

Muscular strength provides the joints with more powerful ligaments and better developed bony parts. After long confinement to the bed from disease, the joints have wasted ligaments, thin cartilages, and the bones are of smaller proportions. Duly exercised muscles influence the size of the bones upon which they act. Thus the bones of a well-developed man are stronger, firmer, and larger than those of a feeble person.

He who has been physically well trained, has both a more complete and a more intelligent use of his muscles. He has acquired the art of causing his muscles to act in concert. Movements once difficult are now carried on with ease. The power of coordination is increased, so that a desired end is attained with the least amount of physical force and nervous energy. In learning to row, play baseball, ride the bicycle, or in any other exercises, the beginner makes his movements in a stiff and awkward manner.

He will use and waste more muscular force in playing one game of ball, or in riding a mile on his wheel, than an expert would in doing ten times the work. He has not yet learned to balance one set of muscles against their antagonists.

[Ill.u.s.tration: Fig. 40.--The Standard Special Chest Weight.

A convenient machine by means of which all the muscles of the body may be easily and pleasantly exercised with sufficient variations in the movements to relieve it of monotony.

A s.p.a.ce 6 ft wide, 6 ft deep, and 7 ft high nearly in front of the machine is required for exercise.]

In time, however, acts which were first done only with effort and by a conscious will, become automatic. The will ceases to concern itself. By what is called reflex action, memory is developed in the spinal cord and the muscular centers (sec. 273). There is thus a great saving of actual brain work, and one important cause of fatigue is removed.

83. Effect of Exercise on Important Organs. The importance of regular exercise is best understood by noting its effects upon the princ.i.p.al organs of the body. As the action of the heart is increased both in force and frequency during exercise, the flow of blood throughout the body is augmented. This results from the force of the muscular contractions which play their part in pressing the blood in the veins onward towards the heart. Exercise also induces a more vigorous respiration, and under increased breathing efforts the lung capacity is increased and the size of the chest is enlarged. The amount of air inspired and expired in a given time is much larger than if the body were at rest. The blood is thus supplied with a much larger amount of oxygen from the air inhaled, and gives off to the air a corresponding excess of carbon dioxid and water.

Again, exercise stimulates and strengthens the organs of digestion. The appet.i.te is improved, as is especially noted after exercise in the open air. The digestion is more complete, absorption becomes more rapid, the peristaltic movements of the bowels are promoted, and the circulation through the liver is more vigorous. More food is taken to supply the force necessary for the maintenance of the mechanical movements. Ample exercise also checks the tendency towards a torpid circulation in the larger digestive organs, as the stomach and the liver, so common with those who eat heartily, but lead sedentary lives. In short, exercise may be regarded as a great regulator of nutrition.

Exercise increases the flow of blood through the small vessels of the skin, and thus increases the radiation of heat from the surface. If the exercise be vigorous and the weather hot, a profuse sweat ensues, the rapid evaporation of which cools the body. The skin is thus a most important regulator of the bodily temperature, and prevents any rise above the normal which would otherwise result from vigorous exercise. (See secs.

226 and 241).

84. Effect of Exercise upon the Personal Appearance. Judicious and systematic exercise, if moderately employed, soon gives a more upright and symmetrical figure, and an easier and more graceful carriage. Rounded shoulders become square, the awkward gait disappears, and there is seen a graceful poise to the head and a bearing of the body which mark those whose muscles have been well trained. A perfectly formed skeleton and well-developed muscles give the graceful contour and perfect outline to the human body. The lean, soft limbs of those who have never had any physical education, often look as if they belonged to persons recovering from sickness. The effects of sound physical exercise are well exhibited in the aspect of the neck, shoulders, and chest of one who has been well trained. This is noticeable in gymnasts and others who practice upon the horizontal bar, with chest weights, dumb-bells, and other apparatus which develop more especially the muscles of the upper half of the trunk.

[Ill.u.s.tration: Fig. 41.--Young Woman practicing at Home with the "Whitely Exerciser." (From a photograph)]

Exercise improves the condition of the tissues generally. They become more elastic, and in all respects sounder. The skin becomes firm, clear, and wholesome. Hence, every part of the surface of the body rapidly takes on a change in contour, and soon a.s.sumes that appearance of vigor and soundness which marks those of firm physical condition. The delicate, ruddy aspect of the complexion, the swing about the body and the bearing of the head and shoulders, of young women whose physical training has been efficient, are in marked contrast with those characteristics in persons whose education in this respect has been neglected.

85. Effect of Unsuitable or Excessive Exercise. But exercise, like everything else which contributes to our welfare, may be carried to excess. The words excessive and unsuitable, when applied to muscular exertion, are relative terms, and apply to the individual rather than to amount of work done. Thus what may be excessive for one person, might be suitable and beneficial to another. Then the condition of the individual, rather than the character of the muscular work, is always a most important factor.

Breathlessness is, perhaps, the most common effect of undue exertion. Let a middle-aged person, who is out of practice, run a certain distance, and he is soon troubled with his breathing. The respirations become irregular, and there is a sense of oppression in his chest. He pants, and his strength gives out. His chest, and not his legs, has failed him. He is said to be "out of breath." He might have practiced dumb-bells or rowed for some time without inconvenience.

The heart is often overstrained, and at times has been ruptured during violent exertion, as in lifting an immense weight. The various forms of heart-disease are common with those whose occupations involve severe muscular effort, as professional athletes and oarsmen. Haemorrhages of various kinds, especially from the lungs, or rupture of blood-vessels in the brain, are not uncommon results of over-exertion.

Excessive repet.i.tion of muscular movements may lead to permanent contractions of the parts involved. Thus sailors, mechanics, and others frequently develop a rigidity of the tendons of the hand which prevents the full extension of the fingers. So stenographers, telegraphers and writers occasionally suffer from permanent contractions of certain muscles of the arm, known as writer's cramp, due to their excessive use. But the accidents which now and then may result from severe physical exertion, should discourage no one from securing the benefits which accrue from moderate and reasonable exercise.

86. Muscular Fatigue. We all know how tiresome it is to hold the arm outstretched horizontally even for a few moments. A single muscle, the deltoid, in this case does most of the work. Even in a vigorous man, this muscle can act no longer than four to six minutes before the arm drops helpless. We may prolong the period by a strong effort of the will, but a time soon comes when by no possible effort are we able to hold out the arm. The muscle is said to be fatigued. It has by no means lost its contractile power, for if we apply a strong electric stimulus to it, the fatigue seems to disappear. Thus we see the functional power of a muscle has a definite limit, and in fatigue that limit is reached.

[Ill.u.s.tration: Fig. 42.--A Well-Equipped Gymnasium. (From a photograph.)]

The strength of the muscle, its physical condition, the work it has done, and the mental condition of the individual, all modify the state of fatigue. In those difficult acts which involve a special effort of the will, the matter of nerve exhaustion is largely concerned. Thus, the incessant movements in St. Vitus' dance result in comparatively little fatigue, because there is no a.s.sociation of the brain with the muscular action. If a strong man should attempt to perform voluntarily the same movements, he would soon have to rest. None of the movements which are performed independently of the will, as the heart-beats and breathing movements, ever involve the sensation of fatigue. As a result of fatigue the normal irritability of muscular tissue becomes weakened, and its force of contraction is lessened. There is, also, often noticed in fatigue a peculiar tremor of the muscles, rendering their movements uncertain. The stiffness of the muscles which comes on during severe exercise, or the day after, are familiar results of fatigue.

This sense of fatigue should put us on guard against danger. It is a kind of regulator which serves in the ordinary actions of life to warn us not to exceed the limits of useful exercise. Fatigue summons us to rest long before all the force of the motor organs has been expended, just as the sensation of hunger warns us that we need food, long before the body has become weak from the lack of nourishment.

We should never forget that it is highly essential to maintain an unused reserve of power, just as a cautious merchant always keeps at the bank an unexpended balance of money. If he overspends his money he is bankrupt, and the person who overspends his strength is for the time physically bankrupt. In each case the process of recovery is slow and painful.

87. Rest for the Muscles. Rest is necessary for the tissues, that they may repair the losses sustained by work; that is, a period of rest must alternate with a period of activity. Even the heart, beating ceaselessly, has its periods of absolute rest to alternate with those of work. A steam-engine is always slowly, but surely, losing its fitness for work. At last it stops from the need of repair. Unlike the engine, the body is constantly renewing itself and undergoing continual repair. Were it not for this power to repair and renew its various tissues, the body would soon be worn out.

This repair is really a renovation of the structure. Rest and work are relative terms, directly opposed to each other. Work quickens the pulse and the respiration, while rest slows both. During sleep the voluntary muscles are relaxed, and those of organic life work with less energy. The pulse and the respiration are less frequent, and the temperature lower than when awake. Hence sleep, "tired Nature's sweet restorer," may be regarded as a complete rest.

The periods of rest should vary with the kind of exercise. Thus exercise which produces breathlessness requires frequent but short rests. The trained runner, finding his respiration embarra.s.sed, stops a moment to regain his breath. Exercises of endurance cause fatigue less quickly than those of speed, but require longer rest. Thus a man not used to long distances may walk a number of hours without stopping, but while fatigue is slow to result, it is also slow to disappear. Hence a lengthy period of rest is necessary before he is able to renew his journey.

88. Amount of Physical Exercise Required. The amount of physical exercise that can be safely performed by each person, is a most important and practical question. No rule can be laid down, for what one person bears well, may prove very injurious to another. To a certain extent, each must be guided by his own judgment. If, after taking exercise, we feel fatigued and irritable, are subject to headache and sleeplessness, or find it difficult to apply the mind to its work, it is plain that we have been taxing our strength unduly, and the warnings should be heeded.

Age is an important factor in the problem, as a young man may do with ease and safety, what might be injurious to an older person. In youth, when the body is making its most active development, the judicious use of games, sports, and gymnastics is most beneficial. In advanced life, both the power and the inclination for exercise fail, but even then effort should be made to take a certain reasonable amount of exercise.

Abundant evidence shows that physical development is most active from thirteen to seventeen years of age; this manifests itself clearly by increase in weight. Hence this period of life is of great consequence. If at this age a boy or girl is subjected to undue physical strain, the development may suffer, the growth be r.e.t.a.r.ded, and the foundation laid for future ill health.