Sit back-to-back with a partner, approximately 12 inches apart. One person holds a medicine ball (or unweighted ball) in both hands with shoulders relaxed, elbows bent, and arms pulled close to the sides of the body. Place your knees and feet about 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, but make sure you are not leaning on your partner's back (pictured).
EXHALE: Keep your heels on the floor, abs engaged and back straight as you twist (from the waist) toward each other. Pass the ball to your partner. INHALE: Both people return to the starting position, facing forward. EXHALE: Twist to the opposite side and receive the ball from your partner. INHALE: Return to the starting position, facing forward, to complete one rep.
Keep your abs pulled in, shoulders relaxed, and feet down at all times. Focus on twisting from the waist, allowing your upper torso and arms to turn with you. Keep your back long and flat at all times. Do not lean on your partner. If your backs touch, scoot farther apart.
Make it easier: Don't lean back as far. Use a lighter weight or no weight. Limit your range of motion.
Make it harder: Lean back and/or twist farther. Lift one foot off the floor to increase the intensity and balance challenge.
Muscles Worked: Abs, Obliques