At first glance, the human body seems correct, but it is not. If the body is divided into two halves by the medial plane in the front-to-back direction, you will find many differences in the fine structures of the two halves. The shape is asymmetrical, and some are more obvious, which can be easily seen directly. For example, people who are accustomed to working with the right hand (most people use the right hand) have more activity in the right hand and more opportunities for exercise, so the bones and muscles of the right hand are thicker, more developed. , and stronger than the left hand, and also much larger, and the right hand is longer than the left (about 1 cm).
In daily life, most people are used to working, writing, holding chopsticks, carrying things, playing ball, etc. with their right hand. According to statistics, about 95-98% of people are right-handed. Physiology calls this phenomenon "right-handedness." The right hand is larger than the left in strength, volume or mass. The right hand is more developed than the left, and this even affects the development of the right leg than the left leg. So why do people habitually use the A with the right hand? According to biological research, people are accustomed to using the right hand, which is gradually developed through long labor. In the early Stone Age, people fought in groups with stone axes and spears in their hands with wild animals. In combat, people instinctively bend their left hand to protect the heart on the left side chest, and with their right hand they rush at the beast with weapons. This can also be seen on the frescoes of Ancient Greece, which remained more than a thousand years ago: people hold a spear in their right hand and a shield in their left.
For many years, people often use their right hand, even sometimes children use their left hand to write or eat with chopsticks, but teachers and parents always ask him to change it. Gradually, the “right-wing” phenomenon becomes not only an acquired habit, but also an innate heredity. Someone once conducted such an experiment. The child, who was only 4 months old, was put on a chair every day for a certain amount of time. There were many toys in front of the chair. He was found to be reaching out his hands to take toys. 124 times, of which 74 times with the right hand, 50 times with the left hand. Later, the number of times the child uses the right hand gradually increases, so that when the toy is placed next to the left hand, he also takes it with the right hand.
In the human body, the nerve pathways leading to the brain from various departments intersect in the middle, that is, the right hand is controlled by the left hemisphere of the brain, and the left hand by the right hemisphere of the brain. brain. Since people often use their right hand, gradually the sensitivity of the left hemisphere of the brain becomes slightly higher than that of the right, which in turn encourages people to use the right hand more often, gradually making the right hand stronger than the left. To achieve the most balanced development, it is also necessary to pay due attention to the use of the left hand in sports and work.