Why do people suffer from black-outs?!
Question:
Why do people suffer from black-outs?
Answers:
http://www.healthed.msu.edu/fact/blackou...
Or are you thinking of passing out?
Passing out usually occurs when not enough oxygen is getting to the persons head.
If you lock your knees (ex.) no blood is getting to the persons head, then when they unlock there knees, all the blood rushing up their. Another reason for passing out, a rush of blood to there head.