Stack and hold, obliques on fire.
Push your hips up toward the ceiling, the second they sag the hold is over.
Holding your body in a straight line on one forearm makes the obliques on the down side work continuously against gravity trying to fold you in half. There is no movement to hide behind, just a braced hold where the tension never switches off until the timer does. Working one side at a time also shows you instantly which side of your core is the weak link.
Same movement, different name. Forearm down, feet stacked, hips lifted into a straight line and held for time. Whatever you call it, the standard is identical, hips high and body in one line.
Start with 20 to 30 seconds per side with perfect position and build toward 45 to 60. A shorter hold with hips high beats a long one where you sag through the last half.
The obliques holding you up are fatiguing, which is the point, but a sagging hold trains nothing. Push your hips toward the ceiling, and when they will not stay there, end the set and rest rather than grinding out a droop.
