not to many months ago I did the same thing to a friend who wanted to see what it was like, I had him sit down and close his eyes, fully relax and just let go, the only condition was that he held one hand up and would tap three times when he thought he would be near passing out.
Well, my other frind their timed us, and it took less than five seconds. At three he tapped my arm once, but passed out, unable to even tap again.
This looks like pretty much the same situation at the same speed.