On the banks of the Nile River in the mysterious land of Egypt, a group of women who had just drawn water from the river and were carrying water jars on their heads walked steadily towards the desert in the suburbs. The line of women, which stretched for over a kilometre, was swayed by the gusts of wind, looking like a group of fairies descending to earth, which was a beautiful and spectacular sight. At this moment, a question suddenly popped into my mind: Why don't they carry things by hand or on their shoulders? After all, a water jar weighs at least 10 kilograms. Isn't it tiring to carry it on their heads? In fact, carrying things on the head is not unique to African women. In Asian countries such as Korea, Myanmar, and Nepal, women also have the habit of carrying things on their heads. We can't help but ask: Is carrying things on the head more energy-saving than other manual carrying methods? Of course, this phenomenon has also aroused the interest of scientists.
After analysis, scientists found that this method of carrying really has advantages in mechanical structure. Firstly, women in those places like to braid their hair into many small braids and then tie them up. Before carrying things on their heads, they will also pad their heads with cloth-tied pads to increase the area where the objects press on their heads. Compared with carrying things on the shoulders or by hand, carrying on the head has a larger bearing area, so the pressure on the head is relatively smaller. Moreover, this method makes the load on the head more even, which can also increase the friction between the head and the objects to prevent the objects from slipping off. Secondly, the human body is a basically symmetrical structure. Placing objects on the head of a person means that the gravity axis of the objects coincides with the gravity axis of the human body. Compared with carrying things on the shoulders or by hand, it can greatly reduce the force needed by the human body's muscles to maintain balance. At the same time, scientists found that this method of carrying is more energy-saving and efficient in terms of energy utilization. We all know that when people walk, their bodies will produce a wave-like movement with ups and downs. And the energy consumed in walking is mainly when lifting the body with each step. To reveal the secret of less energy consumption in carrying things on the head compared with other manual carrying methods, scientists conducted relevant research and analysis. Their research results showed that when a person walks, various parts of their body will move up and down to different degrees, but the movement amplitude of the head is much smaller than that of other parts of the body. This is because the human body's physiologically curved spine is like a spring, which greatly reduces the vibration of the important organ of the brain during each step, protecting the brain. Therefore, the secret was revealed: precisely because the movement amplitude of the head is smaller, the movement amplitude of the objects placed on the head is also smaller, so the energy consumed by the human body to lift these objects with each step is also less, thus unintentionally saving physical strength. Moreover, scientists even calculated that if a person carries a weight no more than 20% of their own body weight on their head, the energy consumed is almost the same as that without carrying a load. This is also the reason why women on the banks of the Nile River can carry water jars on their heads for long distances and walk them back to their homes in the desert. Their ancestors discovered this secret in long-term labor and utilized it, and this method of carrying has been passed down from generation to generation and become a common method of carrying.
Adolescents' bodies are growing rapidly, and their entire skeletons, including the spine, are also growing rapidly. In particular, the soft cervical spine has not yet developed maturely, so it is not suitable to carry heavy loads, let alone try the method of carrying things on the head mentioned above. At the same time, the whole society should pay more attention to the growth of adolescents and do our best to "lighten the burden" on their shoulders.