Patient's question:
According to what I read, a 4-month-old baby's movements should exhibit symmetry. What does this mean? Does it mean that the baby's two arms must move exactly the same way at all times, and the two legs must also move exactly the same way? But my baby isn't like that. She might bend both arms, or extend both arms, and the same goes for her legs. Is this normal?Doctor's answer:
Hello, it's normal for children to be like this, don't get anxious. The principle of motion economy refers to the economic law that allows a person to achieve the greatest work effect with the least amount of effort when operating tasks. By studying and applying this principle well, we can find many actions that do not comply with it in factories, which naturally leads to low efficiency and easy fatigue among personnel. If both hands move in one direction, it will cause a shift in the body's center of gravity, and maintaining this balance will result in mental and muscular fatigue. The most labor-saving way of operation is when both hands move symmetrically in opposite directions.