Turtleling.
That's what you need, ONCE.

That's what it is called when you suddenly hit that point of no return; no forward movement and somehow your foot is still clipped in.

Ker-PLUNK....you turtle....flop over like a big old helpless turtle on his shell.

It happened to me ONCE. Usually never happens after that because you remember how embarrassed you were when it happened the first time. Of course it always seems to happen when someone else is around to see you make a fool of yourself!