Re: Tabata planks
If 20:10 is a rep scheme for holding planks, that's fine, especially with the planks where you lift an arm and a leg. 20 second holds in this case would be challenging to a lot of people (plus the cumulative effect of the rounds adds to the tension).
But that's just as a time scheme... I don't think anyone can kid themselves into thinking that they're getting the benefits of the Tabata protocol through doing an isometric exercise like that. Maybe I'm wrong but tabata as all out balls to the wall intense bursts doesn't correspond to literal motionlessness.