Hold a medicine ball (or dumbbell) and sit on the floor with shoulders relaxed, arms extended, legs hip-width apart, heels on the floor, knees bent and back straight. Pull your abs in tight, and with a straight back, lean back from the hips until you feel your abs engage. Hold that position and lift both feet off the floor (pictured).
INHALE: Keeping feet off the floor, abs engaged, and arms extended, twist from the waist to the left side. EXHALE: Twist back to the center (starting position). INHALE: Twist to the right side. EXHALE: Return to the starting position to complete one rep.
Keep your abs pulled in, shoulders relaxed, and feet off the floor. Focus on twisting from the waist, allowing your upper torso and arms to turn with you. Keep the lower body as still as possible. Keep your back long and flat at all times.
Make it easier: Don't lean back as far. Use a lighter weight or no weight. Hold the weight closer to your torso.
Make it harder: Lean back and/or twist farther.
Muscles Worked: Abs, Obliques