Our body's natural fail-safe mechanism

I went to accompany my brother to the hospital today, to go and check his torn ligament tissue in his left knee. And this is what I have learned today.

Do you know, that our body has a natural fail-safe locking mechanism? Imagine this: You are running, or jogging, or playing futsal, whatever. Suddenly, you twist your ankle, or torn your ligament as such in my brother's case. Your body will sense such occurrences immediately, and without even telling your brain, that particular area of your body will go into lock down. The muscles and tissues surrounding the hurt area will begin to be alerted of such injury, and began to swell, causing the movement in that area to be limited, and possibly even to be shut down immediately. This is to resist your body to inflict further damage, and to protect that injured area from further injuries. As a result, the injured area is now protected by its very own cocoon of protection.

Cool heh?