The development of children's movements in A and B follows three principles, namely, ① Head-to-tail (top-down) principle: the earliest movement of children's development is head movement, followed by trunk movement and finally foot movement. Any child's movements always develop in the direction of looking up, turning over, sitting, climbing, standing and walking; ② Near-far (from center to edge) principle: The muscles and movements close to the body center (trunk) always develop first, and the movements of limbs far away from the body center develop last. Taking the arm as an example, the shoulders and upper arms mature first, followed by elbows, wrists, hands, and finger movements develop last. ③ The principle of wholeness-part-wholeness: The movements of newborn babies are mixed.

General and undifferentiated large muscle groups exercise. For example, when a 4-or 5-month-old baby wants to hold the bottle in front of him, he often uses his arms or even his whole body instead of his hands, and his whole body is jumping when he cries.