Infants always stirrup and make strength may be related to physiological factors, but may also be due to pathological factors, such as lack of vitamin D, gastrointestinal dysfunction, and so on. 1. Physiological factors: infants always stirring their legs to make strength, if the mental state is relatively good and normal development, it may be a normal physiological phenomenon. This is due to the fact that at this stage of the baby’s growth is relatively fast, the cells will keep dividing resulting in faster growth of bones, muscles and skin, so the baby will keep stretching his body to make himself reach a comfortable state. 2. Pathological factors (1) Vitamin D deficiency: If the infant always stirs his legs to make strength, and accompanied by pillow baldness, night terrors, excessive sweating, etc., it may be due to the lack of vitamin D. The lack of vitamin D can lead to neurological problems. Vitamin D deficiency in infants can lead to increased neural excitability, thus showing stirring legs and making strength. (2) gastrointestinal dysfunction: gastrointestinal dysfunction in the organism, will lead to the baby’s stomach is uncomfortable, usually the baby will be through the stirrups and other actions to show their discomfort. Infants always stirring their legs to make strength, it is recommended to consult a doctor in time to exclude pathological factors, so as not to affect the normal growth and development of infants.