No, the CSF here is not "Central Security Force" or "Critical Success Factor" or "Connected Services Framework". It's something new. Actually I happened to have my first encounter with this new CSF this morning. Here it goes:
I have been doing early morning workouts (jogs, exercises etc.) since I was four or five - that makes around 20 years now. Getting up at 4 or 5 in the morning is quite a routine.
But, today something unusual happened. This had never happened with me till date.

I was carrying out with my normal morning exercises. 5:20 AM. I was doing pilates - bent backwards and stretched myself backwards as much as I can. Similar to what appears in the image to the left here. But I was standing.
I remained in the position for about 10 seconds and then I sprang back to my normal standing position. I did it at once, with a jerk. Blunder! Now, I could't see anything, I couldn't stand, I didn't have any control over my body, felt powerless and helpless. I just sat on the stairs of the stadium and then collapsed. I fainted. I regained conciousness after maybe 5-6 seconds or so. Though I got up and continued with my next set of exercises, but I knew something went wrong, couldn't push this idea out of my head. You see, I was consciously unconscious - I knew I am unconscious. Went back to the room and told papa about this with a worried face. Papa being a doctor, so cool.
(Hello! I fainted and he is kewl?)
Replied, "Nothing to worry. You just shouldn't have got back with a speed. You should have done it a bit slowly and smoothly."
"No Papa, that's not the concern. Why did it happen?"
"It happened because of CSF - Cerebral Spinal Fluid. It is a fluid in our head around the brain. When you leaned backwards, it got collected towards that portion of head. It takes sometime for the fluid to float around. So, when you got back up from the stretched back, you didn't give time to the fluid to be back to normal - you collapsed."
"Are you sure, there is nothing to worry? (I am really worried actually) "
"Nah re! but just keep this in mind for future."

I recalled "Hmmm... That's why he never allowed me to spring back while doing this earlier."

Since morning, I am "Googled up" about this. Got a lot of information. If someone wants to learn more, Here it is:
CSF - Cerebrospinal fluid (Wiki) OR CSF - Answers

So next time if something similar happens to you, don't worry, just try to get your CSF to normal position :)

Till then ... Keep exercising!
But a thumb rule while doing any exercise: "Never do anything with a jerk. No sudden or abrupt movements. Each and every action should be smooth - even breathing."