1
Sit on the floor, knees bent, lean back slightly to engage your core.
2
Lift your feet off the floor for more difficulty, or keep them down for stability.
3
Rotate your torso side to side, touching the floor (or a weight) beside your hip each time.
4
Keep your chest up and spine long — don't round your back.
5
Move with control, driven by your obliques, not just your arms.
