Plank on the ball, pull your knees in, control the roll.
Keep hips level the whole way, no spiking up at the top of the tuck.
This is a plank that moves: with your shins on the ball, your abs hold the body line while your knees draw the ball in, then fight even harder as the legs extend and the lever grows long again. The ball adds a sideways wobble no fixed surface can imitate, so your core corrects constantly in every direction. It sits a clear level above static planks and a level below pike variations.
The pike, by a distance. Pull-ins bend the knees, which shortens the lever, pikes keep the legs straight and send the hips high. Own crisp pull-ins before you attempt pikes.
Slow down, shorten the range, and set your hands a little wider for a stronger base. Drift means your core is not yet controlling the roll, so reduce the challenge until it does.
Deep through your abs, both during the tuck and the slow extension back out. If your lower back aches instead, your hips are sagging as the legs extend, so shorten the range.
