Well, that depends what you use as a ligature. In my case, I tried with a necktie and it thigtened well when I kneeled forward. I tested it about 15 seconds.
In any case, you need to put the anchor point in a considerable height. In my case, the anchor point in my experiment was a necktie loop at my bedroom door. I knot the second necktie to the first one and then lean foward.