Our Muscles—Mystery of Creation
OUR muscles, which we use in so many ways and for ever so many purposes, we usually just take for granted—that is, until we do something that makes them ache. But what do you know about how they function?
For years there have been researchers who have been intrigued by the mystery of muscle action. They have studied the muscles in the hope of understanding just what takes place when the muscles go to work. Muscle action has presented a real challenge to these men.
A leading scientist in the field, the Hungarian chemist Szent-Györgyi, stated some twenty-five years ago: “The problem of muscular contraction is still unsolved.” Fourteen years later another investigator stated: “We still cannot answer the fundamental question: ‘How does the molecular machinery of the muscle convert the chemical energy stored by metabolism into mechanical work?’” And recently Professor Ville of Harvard University stated in his book Biology: “Physiologists and biochemists have been attempting for many years to solve the problem of how a muscle can exert a pull, but the actual chemical and physical events that occur in muscle contraction are still a matter of conjecture rather than established fact.” But many interesting things have been learned along the way.
Muscle Characteristics
Muscles are among the things that set man and the animals apart from most plants in that they impart the ability to move. And not only do muscles enable us to get about on our feet and do many things with our hands, but many of the vital functions of our bodies depend largely upon our muscles. Breathing, the circulation of the blood, digestion, excretion and reproduction, all are dependent on our muscles, of which there are from five to six hundred or more.
Muscles account for 40 to 50 percent of the body’s weight. They consist of about 75 percent water, 20 percent protein, 2 percent fat, as well as various kinds of minerals or salts. Individual muscles vary in length from about an eighth of an inch, in the inner ear, to eighteen or more inches, in the legs. Perhaps the tiniest muscles are those that cause our hair to stand on end when we are frightened or that give us goose pimples when we shiver from the cold.
A popular science publication once stated that “one of the greatest secrets of nature is the mystery of the muscles.” Some muscles can lift a thousand times their own weight; some can exert a tension of forty pounds per square inch of their cross section. The muscle of a clam can keep a viselike grip for hours without apparently consuming any energy. The muscles of our hearts and our lungs work from the cradle to the grave without stopping. In Methuselah’s case that was for 969 years! (Gen. 5:27) Some of our muscles can contract and relax in a fraction of a second. The muscles of certain insects are able to move or vibrate at fantastic rates—from 55 times a second in the case of some beetles, to as many as 1,046 times a second in the case of the midge, a tiny fly.
Three Kinds of Muscles
There are three kinds of muscles in our bodies: (1) Voluntary muscles, which include the skeletal and facial muscles; (2) involuntary muscles, which are found among the muscles in the blood vessels, intestines, stomach, bladder and uterus, and (3) heart muscle.
Voluntary muscles are also termed “striated” or striped muscles, because under a microscope they show alternating light and dark stripes or ridges running crosswise. Most of these muscles are long and narrow, as in the arms and legs; but others are sheetlike, as those of the abdomen and the back. Voluntary muscles are endowed with a rich nerve and blood supply so that they can accomplish their purpose. Some, such as respiratory muscles, might be said to be both voluntary and involuntary. We use them voluntarily when we take a deep breath, but most of the time, and especially when we are asleep, they work without any volition on our part.
By way of contrast, involuntary muscles are termed “smooth,” for they are without these striped ridges. With the aid of the electron microscope a striking and purposeful difference has been discovered between the structure of the voluntary and the involuntary or smooth muscles. In smooth muscles the filaments that do the actual work of contracting are arrayed in parallel, overlapping one another, and at an angle of as much as 10 percent to the long axis of the muscle cell. This oblique arrangement of the filaments in smooth muscles may give them as much as ten times the strength that they would otherwise have and so enables them to sustain forceful contractions over long periods of time. On the other hand, the way the filaments lie in voluntary or striped muscles, in series or end to end, permits them to move with greater velocity or speed. And the amount of contraction can be far greater than in smooth muscle. This is just what these voluntary muscles need to do to serve man well. They surely give evidence of a wise Designer.
The muscle of the heart is in a class by itself. Because of its great work load it has a special kind of construction, making it the strongest muscle in man. In woman, only the muscle of the uterus, needed to expel a baby at birth, is said to be stronger. Heart muscle is constructed after the pattern of voluntary muscle, but it functions as an involuntary muscle.
Muscle Action
The voluntary or skeletal muscles, which are fastened by means of tendons or sinews to the bones, actually serve as bridges across the joints. It is the group of muscles between the elbow and the shoulder that move the forearm, even as the muscle group between the elbow and the wrist move the hand. A group? Yes a group is needed to make possible the different kinds of movement, and that by means of the tendons. Tendons, however, are not to be confused with the ligaments that link bone to bone and which cannot stretch. When ligaments are stretched, there is a painful sprain.
As for the muscular action itself, there are only two kinds that muscles can perform: They can (1) pull, contract or become tense and (2) relax. They can never push.
Mainly, our voluntary muscles come in pairs or pairs of groups. Groups of two or three are paired to act as antagonists to each other. For example, the three front flexor muscles are able to flex the forearm, and the two extensor muscles in the back of the upper arm can straighten out the forearm. These “antagonists” always cooperate. Thus when the one contracts, the other relaxes, making possible the other’s contraction. This, of course, requires coordination of the nerves, the sending of signals to the one set of muscles to contract and at the same time to the opposing group of muscles to relax.
A muscle consists of sheathed fibers the diameters of which may range from 1/250th to 1/2500th of an inch, and these may be the full length of the muscle. The fibers are made up of parallel elements, 1/25,000th of an inch in diameter and these, in turn, consist of parallel actin and myosin filaments. It appears that the key to muscle action lies in these actin and myosin filaments. It is now understood that when a muscle contracts, one of these slides past the other.
Muscular activity consumes oxygen and nitrogen, causing a demand of these from the blood, and at the same time results in an increase of waste products, namely, carbon dioxide and lactic acid, which the blood carries away. It is the presence of lactic acid in the muscle that causes one to feel tired. The bloodstream serves both to feed the muscles and to carry away their waste products and does it without confusing the two. While this much is known, what remains to be understood is just how nerve force is able to change the products of food metabolism stored in the muscle to mechanical energy. That is still a great mystery to man.
Muscle Tone
Our voluntary muscles are never fully relaxed. There is always a slight tension or ‘tone,’ and this tension makes it possible for muscles to go quickly into action. Both rapidity of movement and smoothness of movement depend upon this muscle tone. Proof of the tone is seen when a tendon, which fastens a muscle to a bone, is cut. The muscle retracts.
However, muscle tone is not achieved by the entire muscle being always somewhat tense. In muscle fibers the rule of “all or nothing” applies. That is, the individual fibers do not respond at all until a certain degree of nerve stimulus is applied, and then they contract all the way. Then how is muscle tone maintained? By the contraction of small groups of fibers in relays, so that the majority of fibers are resting while comparatively few are active, supplying the needed muscle tone, being on the alert as it were.
This relay activity of the muscle fibers accounts for the fact that we can maintain good posture for a long time without becoming very tired. A certain amount of this muscular activity or tone is required when we sit erect. Standing requires still more. And when it comes to walking, the coordination of many more muscles is involved. No wonder that it takes much time and effort for a child to learn to walk.
Take Good Care of Your Muscles
Not only did the Creator give man hundreds of wonderful muscles but he also commanded the first man ‘to cultivate and take care of’ the garden of Eden. That required man to use his muscles. Man had essential work to do that helped him to keep in fine physical condition. The Creator did not design man for a lazy life. In fact, one of the greatest enemies to strong, healthy muscles is laziness.—Gen. 2:15.
Where a person’s daily occupation does not give him the needed exercise he should be alert to keep his muscles fit in some other way. Climbing stairs instead of always riding the “lifts” or elevators can be of great help; also walking wherever possible instead of using the family auto or public transportation facilities. Push-ups and jogging can do much good too.
Going hand in hand with sufficient exercise is getting enough rest and sleep. Especially helpful is learning to work in a relaxed manner instead of being always keyed up and tense. Needless tension harms both nerves and muscles.
Important also is seeing that the muscles get the right kind of food. That means, among many other things, seeing that one gets enough vitamins and minerals by choosing unrefined foods and eating plenty of fruits and vegetables, raw whenever practical.
What can be done for muscle fatigue, spasms and suchlike ills? Hot, moist applications and massage are among the best remedies, although certain liniments also may help. And, of course, rest is the best treatment of all. If spasms, cramps or severe pain continue, it would be the course of wisdom to consult a physician, especially if these are not located in the limbs.
Nor to be overlooked are psychosomatic factors. If one’s muscles feel tired all the time even though one gets sufficient rest and eats the right kind of food, the problem may well be psychosomatic, the effect of the mind and the emotions upon the body. Not without good reason does the Bible say: “A heart that is joyful does good as a curer, but a spirit that is stricken makes the bones dry”—and, it might be added, it makes the muscles tired.—Prov. 17:22.
Our muscles are truly a wonder, but the details of how they work are still a mystery. Nevertheless, appreciating as much as we do about them should help us to take good care of them.
[Pictures on page 21]
Voluntary Muscle
Heart Muscle
Involuntary Muscle
[Picture on page 23]
Important for keeping muscles fit are exercise, unrefined foods and enough sleep