Why locking your knees could cause you to faint.
In: Biology
It has to do with blood flow.
Unlike your arteries, which are driven by your heartbeat, your veins are much more passive, with no force driving the blood back to your heart. Instead, your veins rely largely on your muscles to squeeze the veins, sort of like a tube of toothpaste or Gogurt.
Locking your knees allows you to stand without using your leg muscles quite as much, which is good for the fact that it saves energy, but bad because without your muscles engaging, you’re losing out on return blood flow back to your heart and brain — and that’s where the risk of fainting comes in.
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