When you stand up immediately after squatting for a long time and feel dizzy, black in front of your eyes, and your legs and feet are numb, this symptom is medically called upright hypotension, or postural hypotension. This is mainly due to the body squatting or sitting for a long time, when suddenly get up, the whole body blood quickly flow to the waist, legs, resulting in a temporary shortage of blood supply to the brain. In addition, the operation of the brain and eyes need to ensure normal blood supply at all times, thus, even a brief shortage of blood supply can cause dizziness and blackness in both eyes. Especially some of the more frail people need to pay attention to the long squatting or sitting, do not violently following stand up, the action should be slow. When people squatting, the distribution of blood in the body some special circumstances. First of all, the two legs are pressed very tightly, the blood vessels flattened, to reach the lower extremities of the blood is relatively less; secondly, because the squatting head slightly forward, to the head of the blood is relatively distributed more.
When you suddenly stand up, the blood vessels of the lower extremities suddenly lifted the compression, so a considerable part of the blood flow to the lower part of the body. In addition, the blood in the body also has a certain weight, when you stand up suddenly, the blood flow due to the attraction of gravity, the role of inertia, also a larger amount of blood flow to the lower part of the body, the distribution of blood to the upper body will be reduced. In addition, when you stand up, your head is also upright, and it is more difficult to eject blood from the heart to the head which is high up. All of this makes the blood to the head relatively less. The human brain is most in need of blood for oxygenation, and a brief reduction in blood supply can cause a person to feel dizzy due to momentary cerebral anemia. In addition, due to the reduction of blood in the head, the blood supply in the eyes is naturally less, so that the phenomenon of dizziness and venus will occur. Meanwhile, anemia and hypoglycemia can aggravate this phenomenon. In this case, there is no need to be overly alarmed, as long as you take some rest and move your muscles and bones, the blood supply to the heart will return to normal, and the symptoms of dizziness and black eyes will disappear.