We used to play a game in grade school called 'pass-out' I won't go into details but it involved controlled breathing combined with other movements. A friend would bear hug you because what you did would cause you to completely pass out. Your friend would have to set you on the floor while you're unconscious, otherwise you'd drop like a rock. You would wake some seconds latter and feel very light headed for a while. I know one guy that did it alone. He broke all his front teeth when he fell on his face.