A side plank on the dome that makes your obliques work to stay put.
Keep your hips high and stacked, fight the dome to stop the wobble.
A side plank already lives or dies on oblique strength, and putting your support arm on the dome means the surface under you shifts while your entire lateral core holds the hips high. The stacked feet and reaching top arm leave the obliques as the only thing between you and the floor. Held for time and trained one side at a time, it earns its place for exposing and fixing left-right core imbalances.
Either works, the setup allows both. Forearm is more stable and kinder to the wrist, straight arm raises the challenge. Pick the one that lets you hold a clean line for the full time.
Very. Lateral core strength is almost never symmetrical, which is exactly why this is done one side at a time. Give the weak side the same time, or slightly more, until the gap closes.
Letting the hips sag toward the floor as the set goes on. The moment your body stops being a straight diagonal, the obliques have stopped doing their job, so end the hold there.
