Roll the ball, twist the core.
Don't let your hips sag or swing, the twist comes from your core not your back.
Planking on your forearms is already an anti-sag challenge, but resting them on a ball that wants to roll turns every second into core work, and steering the ball through circles or side to side makes the obliques control rotation on top of that. One direction at a time, your trunk resists twisting forces while producing small, precise movement. It is a smart upgrade for anyone whose standard plank has gone stale.
Small and controlled, a few inches is plenty. The moment your hips start swinging with the ball, you have made the movement too big and the work has left your core.
Yes, because the ball is now moving on purpose. The static plank fights wobble, this fights wobble while your forearms deliberately create it, so treat it as the progression, not the starting point.
Yes, match your circles or side-to-side reps in both directions. Rotational core work done one way at a time builds an imbalance quickly if you favour your natural side.
