Sit on the floor with feet firmly planted, knees bent, back straight, and hands gripping a medicine ball or dumbbell (not pictured). Extend your arms in front of you, keeping them in line with the shoulders. Keeping your back straight, lean back (hinging from the hips) until you feel your abs engage.
EXHALE: Keeping a perfectly straight back with your abs pulled in tight, rotate your torso to the right as far as you can while maintaining good form (back straight, feet on floor).
INHALE. Return to the center (start position).
Repeat on the opposite side to complete one rep.
Do not round or arch your back. Try to keep your feet planted. Focus on the movement coming from the waist, allowing your upper body and arms to follow.
Make it harder: Use a heavier weight or lean back farther.
Make it easier: Instead of extending your arms in front of you, keep the elbows bent with the medicine ball or weight hugged in close to your torso, and/or don't lean back as far.
Muscles Worked: Abs, Obliques