Plank on a stability ball

Create a stable line through the head, trunk and pelvis and keep abdominal tension for the prescribed time. Breathe normally without letting the lower back sag. Use a steady tempo: control the return phase in particular and avoid relying on momentum. Exhale through the hardest part and inhale as you recover the starting position.

Check that the movement stays stable in both directions and that the torso is not compensating. The goal is controlled loading of abdominals, shoulders and lower back; match resistance and range to a beginner level and never force a painful repetition. On unstable surfaces, master the position with light resistance first; stability should limit difficulty before load does.