Primary muscle: Rectus abdominus (abs), transverse abdominus
Secondary muscles: Erector spinae
Equipment needed: Medicine ball
Starting position: Sit on the floor with your knees slightly bent, feet together. Start with a light ball or hand weight. Sit as tall as possible with your back straight. Hold the ball close to your body between your naval and your rib cage. Use your breath to help engage the muscles of your core. On your exhale, imagine your are tightening a belt around your waist and deepen the contraction.
Keeping your back straight, inhale and slowly rotate your torso to one side. Imagine that the ball is fastened to your torso. It should stay in place through the entire exercise. Do not allow the ball to drop toward the floor. Inhale and then gently exhale while rotating completely to the opposite side. Repeat the movement from side to side.
Three sets of at least 25 repetitions
Next week: Yoga
Amy Carroll is an instructor at the YMCA. She is a certified personal trainer and sports nutritionist.