Hover on all fours, hold it, brace like a board.
Keep your back flat and knees low, do not let your hips pike up.
Lifting your knees an inch off the floor from all fours drops your whole trunk into the core's hands, it has to hold a flat back against gravity with no knees or hips helping. The low hover keeps the position honest, hips level, back like a tabletop, everything trembling but nothing moving. It earns its place as a plank alternative that is harder to cheat and a foundation drill before crawling patterns and moving variations.
It is harder to cheat. The bent-knee hover position punishes hip piking and back sagging instantly, and most people who cruise through planks shake within seconds here.
Just an inch or two. Higher hips shift the work away from your core, the whole challenge lives in staying low and flat.
Because the core is working exactly as intended. Shaking is normal, breathe steadily and hold the position, the trembling fades as you get stronger.
