Legs alternate flexion and extension.
When the baby lies on his back with his legs straight, the mother gently holds the baby's ankle with both hands, pushes his left leg to bend to the abdomen, then restores it, then pushes his right leg to bend to the abdomen, and then puts it down to restore it, doing it twice in a row.
Lower limb relaxation exercise
The baby lies on his back with his legs straight. The mother gently holds the baby's ankle with both hands, gently lifts his leg to 450, and then restores it, doing it twice in a row.