Medical Questions » Other Problems Questions » Question No. 770
| Question: | When I go shopping, and stand for a while waiting to be served, or stand anywhere for a time, I black out. I don' t know when these attacks are coming. Please let me know why this happens. |
| Answer: | Blood is pumped out of your heart, and through the arteries, to every part of your body. To return to the heart, the blood relies upon the action of muscles squeezing on veins as the person moves about during their normal daily activities.
In the veins are one-way valves, that allow blood to travel only towards the heart. When the soft, thin-walled vein is squeezed by the movement of muscles in the arms or legs, the blood moves along the vein, back towards the heart.
If you stand still for any period of time, there is no muscle activity to pump die blood back from the feet and legs. The heart continues to pump out blood, but without the return supply, begins to run out of blood to pump. The brain then becomes starved of blood and switches off, causing you to faint.
When you fall to the ground, blood can easily flow from the legs to the heart because gravity is no longer holding the blood in the legs. The heart pumps properly again, the brain obtains an adequate blood supply, and you recover.
Soldiers who must remain at attention for long periods of time are taught to tense the muscles in their legs, and to rise slightly on the balls of their feet in order to keep their leg muscles working and thus the blood moving back to the heart.
Try not to stand still for long periods, or adopt the soldier' s trick, and keep those muscles working.
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