How good are we aware of the operations of systems and mechanisms that make us walk?

Costly research and development efforts are under way in centers throughout the world seeking to build walking robots by mimicking human mobility. After 14 years of research, automotive firms built Asimo, a robot which can walk bipedally and climb stairs like humans. Even though the moves Asimo could make matched those of a one year old baby, it was still considered a great success for the robot technology.

Hardships encountered during these research projects proved walking to be a great miracle, apart from normal habits of movement. We often become aware of how extraordinary movement is and that the moves we repeat hundreds of times, such as walking, running, bending, sitting and standing, are blessings granted to us only when we see someone who has lost some of their mobility.

That humans can walk bi-pedally is truly exceptional. Most organisms have a front leaning skeletal structure and walk on four extremities; they only stand upright when absolutely required to, since it is very difficult for them. Human ability to stand upright and walk on two legs truly signifies them as special amongst creatures, and sets them apart from all of creation. The lively, regal posture of dexterous bipedal humans constitutes very important evidence showing they are “the most superior of all creatures.”

The multifunctional, flexible nature of our skeletal system enables us to complete very simple moves automatically. Walking seems to be a very easy task, however, it occurs as a calculated outcome of many factors, such as determination of stepping distance, the toning of corresponding muscles of the same and opposite direction, relaxation and contraction levels, and relocation of the body’s gravity center.

Walking takes place via the coordinated works of the locomotor (musculoskeletal) system, motor control system, and balance-coordination system.

Locomotor (musculoskeletal) system

The framework of the human body is built together with 206 bones of variable hardness. With their strong nature and capacity to endure extra weights, bones takes up 20% of a body’s mass, and are the major load bearing part of the body’s structure.

The main part of our skeleton is the vertebral column. It consists of 33 small bones, known as vertebrae, positioned on top of each other. Wear-preventing discs are found in between vertebrae to protect against motion related wearing over time. As the vertebral column holds the weight of the upper body, it is created in a way to keep the body upright. The spinal cord inside the channel that is surrounded by the vertebral column is a very important signaling network providing coordination between the brain and other organs.

Joints and ligaments are among the moving parts of our body. The most important joints for walking are the hips, knees, and ankles. The curvy shape of the foot and its contact to the ground at three spots supports bones against body weight and helps with balance. This is why flat footed people struggle with walking and get tired easily. The curves of our spine at the neck, back and waist regions, and the hips, knee joints, and curvature of the foot, are perfectly shaped for standing upright and walking.

In order to move we need a muscle system along with the skeletal system. Muscles are made up of thousands of contractible muscle fibers. There are more than 6 billion muscle fiber motors in the human body. We walk, run, eat, breathe, talk and do many more moves by using ability granted to muscles. Approximately 35 muscles in each leg, and around 100 muscles in the whole body, function during walking.

Ligaments and tendons are links that secure bones and muscles together; they also help to stabilize joints, thus when standing, joints remain in place without muscles contracting.

Four different mechanisms are involved in walking:

1. Proper upright posture and maintenance of balance during walking
2. Forward motion of body via muscle power
3. Reduction of shock-impact effect while stepping
4. Maintenance of motion with the least amount of energy.

A series of movements is generated in the legs to provide a forward motion and these are constantly repeated. These constant repetitions are called the “walk cycle.” The “passing pose” is defined as the time frame when the leg is in the air, and the contact pose is the phase during ground contact. In the middle of the contact pose, even though body is in balance, because of the forward momentum of the body, balance is lost, thus the body leans forward. Balance is then restored by stepping on the ground with the leg in the air. As a result of this rhythmic loss and restoration of balance, the body moves forward.

In a person standing upright, the center of gravity is in front of the fifth vertebra. At the start of a walk, the body leans forward to carry the center of gravity towards the front; then the initiation of the motion via forward transfer of the power with toes and joints takes place, followed by the lifting of the heels, the bending of the knees, and the lifting of the foot, thus displacing the center of gravity of the forward leaning body towards the front.

Balance should be maintained when one leg is lifted in order to let the other leg carry the load of the body’s weight. The gravitational center of the body is located in the distance between the two legs since each leg is located on the side. Body balance is maintained by the contractions of dorsal muscles located across the side of the stepping foot, working in parallel to support and transfer body weight to the foot via the hip and femoral muscles. These events happen so quickly that we often do not even notice all the complicated processes.

The great Sufi figure Abdul-Qadir Gilani was often asked questions such as, “Master, show us a miracle.” He would stand up to walk three to five steps and sit back down. Everybody was confused, looking at each other. One person among them was heard saying, “Master, excuse us but we can all do that as well.” Gilani replied then, “Is there a greater miracle than walking? You see it, but do not understand.”

Motor control of walking

Bodily motions are controlled via the primary motor centers that are located on the side and cortex region of the brain. These centers are created in a way to prepare and organize motor programs involving body movements, and to integrate them with the proprioceptive memory. This synthesis of information enables the adaptation of motor commands to the present posture of the legs and arms regarding intended moves.

A desire to make a move is a necessary prerequisite for the stimulation of muscles pertaining to it. If we want to hold something, we can easily do it; when we want to raise our arm, our elbows bend; to run or walk, our leg muscles start to move and work. How do all of those moves happen? Is our desire enough to do so? Can the guidance of all the bones and muscles, working together towards the same target, happen by itself or occur via coincidences?

In order for muscles to move, our thoughts must be relayed to them and this is provided by the nervous system and nerve network. There is an amazing communication network present in our body. In case of an intended move, an electric signal is sent by the brain. During this journey, which seems to be complicated, the signal arrives at the spinal cord and then quickly diverts to the corresponding organ. Millions of motors that make up the muscle are stimulated by the electric signal, contracting the fibers instantly upon reception of the signal. In order to do a coordinated move, it is necessary to know the related body organs’ positions and their relations to each other. Millions of transmitters that provide this information have been placed throughout the body. This data come from the eyes, the inner ear’s balance and sensory organs, muscles, joints, and skin. There are billions of micro receptors located in muscles and joints programmed to send instantaneous positions of the body to the central nervous system. In every stage of a move, the positions of the muscles are reported instantly to the command center by these micro receptors inside the muscles. New commands are given to the muscles based on the assessments made here. This way, each second, billions of bits of information can be processed and assessed.

The cerebellum is another center that is in charge of functions such as maintenance of balance during walking and standing, carrying out proper and coordinated moves with visual control, providing coordination among muscle groups, promptly starting and stopping movements, and the maintenance and organization of normal muscle toning. The cerebellum is tasked primarily with hastened muscle activities like running, typing, and talking. Thus, fast moves necessary for the balance system are sustained properly and successively without abnormal oscillations.

Specific motion templates have been programmed in the spinal cord for all muscle-covered regions of the body. Rhythmic movements, such as forward and backward motion of the legs and arms, and coordinated activities of other body parts in tandem with walking, are controlled here. The task to control repeated moves like walking is assigned to the nerve network consisting of the spinal cord, brainstem and cerebellum.

Balance and coordination system

One of the requirements to walk and move is to stay in balance. Despite our advanced musculoskeletal system, without balance, this system of ours would be useless, or even dangerous.. Our balance system, which is in charge of the instantaneous control and fine adjustments regarding our body, is granted to us as a blessing of Divine compassion.

There are three systems that provide data involving the positions of the head and body: vestibular system (the apparatus of the inner ear), visual senses, proprioceptive senses

The vestibular structures are an essential part of the balance system. They are found in the inner ear, and are small and complicated systems. This 6.5 mm diameter wide system is composed of semicircular channels that contain specific fluid and ciliated sensory cells that cover the inner linings of the channels. This system constantly reports information involving our status in the outer world and instantaneous changes to the balance system.

When we move, the fluid inside the semicircular inner ear channels get displaced; this motion vibrates the cilia. This vibration causes an electric signal to generate in the cells. This electrical signal is then transmitted to the cerebellum; received information gets evaluated instantly in the cerebellum. This system is created to function autonomously without our will and control. When this system is impaired, balance disorders occur, such as dizziness.

Information regarding our position in the environment and the relative status of the environment according to us is sent to the cerebellum and brainstem via our visual senses.

Proprioceptive senses are formed via the activities of tension receptors built in muscle fibers, tendons and joint capsules. These are sensitive to motions and positions. These receptors regularly provide information to the central nervous system. The cerebellum receives information from all the muscles and joints of the body, including the eyes. These inputs are analyzed very promptly at the cerebellum, and the relative gravitational position of the body is finely calculated, thus the proper motions of muscles are determined. The resulting response is relayed towards muscles by nerves. These events take place in a time frame that does not even last for a hundredth of a second. We easily walk, run, and do complicated moves without feeling any of these activities happening inside us. Yet the calculations taking place in our body even for a single moment of those movements can fill thousands of pages.

To understand the fascinating side of our ordinary movements, let’s consider a person climbing up the stairs. First, the eyes scan the surroundings, then the three dimensional information of positions acquired from the materials and belongings in the environment are transmitted to the brain. Once received, the information is analyzed and the necessary commands are sent to the target organ from the motor centers of the brain. Commands passing through related tracks and centers finally arrive at the musculoskeletal system. Many factors, like the height of stair steps, length and depth of the foot step, center of gravity and position of the body, are calculated and determined almost instantly.

Proprioceptive signals constantly report the positions of organs, like the arms and legs, to the command center. Inner ear receptors are in charge of the prompt transmission of information necessary for balance, like motion, speed, and direction of the body. These inputs are calculated in milliseconds at corresponding centers in order to maintain the coordination and harmony of the entire body. A person who is running up the stairs may think to jump a couple of stairs. This change of command is rerouted to the locomotor system as a new and different command from the brain. All of these processes are completed in centiseconds. In the mean time, the head, shoulders, and arms are employed for rhythmic oscillations in order to adapt to the overall body momentum.

In conclusion, standing and walking are miraculous and take place via thousands of interrelated activities. Nonetheless, we usually do not notice any of the thousands of processes that are constantly taking place. One hopes that every blessing we have is seen through the window of thanksgiving and appreciation.

Kemal Serce is a professor of veterinary medicine in Bursa, Turkey.

I consist of 217 bones in your body (however, since the bones in the thigh and sacrum areas fuse together in order to form a stronger bone, their number decreases, and the anatomists accept the number of bones as 206). I have 22 skull bones, 33 spinal bones, 24 rib bones, 64 bones in the hands, the forearms, the arms and the shoulder girdle and 66 bones in the feet, the legs, the thighs and the hip area. In addition, I have 6 small ear bones, 1 breastbone and 1 hyoid bone (at the root of your tongue), which make up the total of my 217 bones. It is quite amazing that so many different bones have cooperated with each other and contributed to such a perfect system.

Each piece of my skeleton has been created with special shape and quality that is proper to its place and duty. The bones that protect your brain are flat, whereas the bones in your arms and legs are long and cylindrical; while the bones in your wrists and ankles are short and rounded, your hips and girdles have been made of wide and big bones. The craggy surface of my bones makes it easy for the muscles to attach to them firmly. Each bone has certain durability that protects me from undue weight, flexure, twisting, and pressure. Bioengineers carefully examine my bones that have been created in a perfect form for where they are positioned and for what they do. They take my wonderful structure as a model, and they use it for producing new technology such as buildings or bridges. As you know, constructional engineers have to be very careful in their estimates of material and durability. They have to use different materials for different places, and these points will be exposed to forces like pressure, compression, tensile, or flexure (bending). If the estimates of the materials are not made accurately, the building or the bridge can easily collapse. When you humans build a strong building, it might be too heavy and bulky, resulting in a waste of material and money. Even if you use good quality material, if you do not use it in the right place, all your work might be unusable. Unlike human beings, the Creator has made me such a delicate and well-balanced system, in which you cannot find any material missing or unnecessary or any wrong line in a particular bone. That can only be explained with the boundless knowledge of God the Almighty. He knows exactly how you will be able to do hundreds of different movements in all your life-including running, lying down, jumping, lifting a heavy item, playing sports, writing, and eating. In order to allow you to perform those actions, He has created a perfect design for each piece of my bones and the joints that connect them.

In building my structure, He has used materials in different hardness and durability to make your movements easy. The first material is the bones. Not all bones are the same. Compact bone (dense bone) is found in my hardest parts. For example, the long bodies of the femur, the tibia, and the fibula (bones between knee and ankle) are made of compact bone, and they are very rigid and strong. Softer bones, which look like a sponge, are found at the edges of those long bones and within my flat bones. The second material, my cartilage, is placed at the bone edges and on the joints where, by absorbing excessive pressure, the cartilages are able to prevent damage to the surface of joints and to the nerves that go through the vertebra. My cartilages achieve this thanks to their soft and flexible substance, which also provides a perfect aesthetical quality. In addition, because of this flexibility given by God, cartilages protect the bones from breaking easily (depending on the rigidity of the bones), and they balance your strong and abrupt movements. If it were not for the cartilages on the joints, not only the bony surface would be damaged but also my movements would be mechanical and harsh just like those of a robot. My third material is the ligament, and its main substance, the fibers, that are made of collagen protein. The fibers of this ligament are very strong straps, which hold my bones and cartilages together.

All my joints and tendons that fasten the muscles to my bones are tied up and strengthened by those ligament fibers, which vary in shape, length, and quality. The collagen fibers are also used as the basic substance of my bones and cartilages. Those fibers, which are placed among the cells of the tissues of my bones and cartilages, provide the tissues with strength and durability. The distribution of the fibers in my bones is determined according to the direction and intensity of the pressure coming upon me. To see an example, you can look at the head of my femur (between my knee and thigh) where it makes a joint with the thigh bone. The spread and design of the fibers placed right at this joint requires a flawless calculation, which you can better understand by examining a diagram of it.

Not all my joints are flexible in the same degree. For example, the joints in your skull, which protects your brain and sensorium, resemble the toothed blade of a saw. They are strong joints, which are firmly locked with each other, and they allow no mobility. Of course, it can be no one but God who is able to give my skull such strength and hardness, since He knows exactly how much protection my delicate brain, eyes, and ears need. Moreover, my skull is not shaped simply as a bony capsule; at certain places, God has put little channels for the blood vessels to go through, little cavities for the sensory organs, and a big hole for the spinal cord to connect to the brain. Can any of these be formed by coincidence? The joints between the vertebrae (little bones of your spine) are more movable than the skull and less movable than your fingers. They help to allow you stand upright and sit, twist, and bend or lie down. The joints in my shoulders and legs are freely movable, which enables you to do movements in all directions. Perhaps the most wonderful of all are the joints in your hands! It would not be a distortion to say that-behind all your work to make a discovery or an invention or a new technology-is the skillful creation of my hand joints. Everything that you use with your hands-including all kinds of tools, furniture or appliances, art works, and books-can be produced or utilized only through the perfect ability of my joints to move. If my fingers lacked that great ability to move freely, many of my thoughts or intentions would not be able to be translated into actions.

Your muscles that help in the movement of all my movable parts have to attach to my bones to be supported. While one end of your muscle holds my bone firmly, the other end pulls another bone with the help of the joints. That is how movement in your body occurs and how you can take a step, do exercise, or wave your hand.

Although not as much as the skin, I have a very good ability to renew myself. When one of my bones is broken, if you line up the two pieces exactly in relationship to each other, the bone cells, called osteoblast, quickly divide to produce new cells, fill the gap, and repair the break. Then, I take calcium salts, which harden and strengthen the area, and gain back my health. Calcium is a vital mineral in the growth of bones. When you are a little but growing fetus in your mother’s womb, you need plenty of calcium for your bones to develop. If your mother gets sufficient amounts of dairy products, fish, and green vegetables, there will not be a calcium deficiency. But the good news is that, even if an expectant mother does not get enough calcium, the unborn baby is unlikely to have calcium deficiency. That is because Our Lord God, whose Mercy is infinite, provides baby with calcium by making it be absorbed from the mother’s bones and teeth and ensures the healthy development of the baby’s tiny skeleton. The mother has the willpower to feed herself, but since the baby is helpless, its need is met by the calcium taken from the mother’s body. After birth, the baby has to be nourished well with calcium and vitamin D by means of healthy foods, and it has to have enough exposure to sunlight. In order to maintain my health, my biggest need is calcium salts and vitamin D, a vitamin that needs the body’s exposure to the sun in order to contribute to healthy bone growth. For this reason, you have to take care of me especially at your young age. If you do not get those salts and vitamins, your bones will not develop well, and this could result in skeleton disorders.

The cavities within my bones are called marrow cavities (or medullar space) and they have important duties too. If your bones were filled merely with bony substance, my weight would be too much, and you would not even be able to stand up. Moreover, my bones would not be as strong as they are now. According to calculations with static forces, a rounded iron stick, which is filled, is less durable than the one with a hole in it, and the stick with a hole in it can be bent easily. My long, rounded bones have been designed according to that principle, and they are more resistant to twisting and bending. Another important function of my marrow cavities is to house the production of little red blood corpuscles, which have important duties within the blood. When you are young, all my bone marrows are red, and they produce red blood cells. Then, slowly after the puberty, the bone marrows in my long rounded bones start to turn yellow, get fatty, and produce white blood cells. The spongy bone marrows in my flat bones, however, stay red in color during your entire life, and they keep producing red blood cells.

The shape and size of my bones and their proportions to each other all determine the shape and quality of your body. Although I develop according to my genetically inherited qualities, the loads that you made me carry and outside impacts all affect my development significantly. When you are a baby, my bones start out as cartilages. At young ages when I am just starting to become bony, if I have to carry too heavy things, I start to harden and become bony too fast. This leads to the incomplete growth of the length of your neck bones, and your arms and legs which will remain too short. Playing basketball or volleyball stimulates the growth and elongation of your bones. Mineral salts, vitamin D, and the hormones secreted by the parathyroid gland play role in the ossification of my bones. The elongation of my long bones is achieved by the cell division and formation of new cells in the areas called epiphysis, which are the rounded ends of the long bones. This bone-lengthening process ends after puberty. While the lengthening of bones stops earlier in girls around ages eighteen or nineteen, it continues in boys until the ages twenty-one or twenty-two, which is the reason why men are generally taller than women.

When you were born, all of my components were cartilages, which are very soft and flexible. That is the measure that the all-knowing and all-caring God has taken, to ensure that neither you nor your dear mother gets any harm during your birth. If I became bony before the birth, your mother could die, and many of your bones could break during the birth. However, thanks to the cartilaginous components, which are like plastic, the risk of death and becoming disabled decreases greatly. As you become older, the cartilages are replaced with bone cells, and the accumulation of calcium salts make me hard and bony. The cartilages remained only on the joint surfaces and at the ends of ribs.

Dear Peter! Now it is time to ask a question that might bother you a little: have you ever been at a reopening of a grave? Sometimes in graveyards, when they do not have extra space for new burial, the dead person’s body is buried next to a body that belonged to a family member. When the grave is reopened, you can clearly see that, except for the newly buried body, all parts of the other dead body have been mingled with the earth. You can see that only my skull and other bone components have remained without decaying. After a very long time, those bones will decay too but much later than my other tissues. In the past, when the Holy Qur’an was just being revealed, some people refused to believe in God and the Day of Judgment, and asked: “Who is going to resurrect those decayed bones?”(Qur’an 36:78). The following verse is an answer: “Say, ‘He who created them in the first place will give them life again: He has full knowledge of every act of creation’” (Qur’an 36:79). In many other verses of the Qur’an, which deal with both the first creation and the Judgment Day, also mention decayed or dried bones, which still exist after many years. This means that God wants to draw your attention to the bones of your body! Perhaps, He is saying: “O, Peter! I created your bones, your joints, and your whole skeleton flawlessly. I took all measures for you to be able to live your life perfectly; to the littlest details, I created a delicate body, mind, and soul free of defects or faults. When I created you that perfectly, do you think I took something else as a model, or applied someone else’s plans? Not at all! Therefore, I, who created you out of nothing with my infinite knowledge and might, will of course be able to recreate you!”

Well, Peter! That is how I understand my Creator and the message of His Holy Book, which appeals to all of humanity. Your ability of comprehension and appreciation is more perfect than mine. Therefore, each time you move your body or body parts, just think of the wonderful pieces of bone accompanying and supporting your organs. Reflecting on them for some time will gain you a fresh view of life. That is what I wish as your skeleton!

Irfan Yilmaz is a professor of biology at Dokuz Eylul University, Izmir, Turkey.