Want to see a firmer, flatter tummy in less time? Try revving up your workout with a stability or fitness ball. Numerous studies have found that you use more abdominal muscle fibers when doing a crunch on a stability ball compared to doing it on the floor. So do these core exercises to effectively strengthen and sculpt your midsection twice a week, and you'll starting seeing results in as little as two weeks.

Stability Ball Crunch

Steps:

1. Lie faceup on a stability ball with your back completely supported, knees bent and aligned over ankles, and feet flat on floor. Tighten buttocks muscles to stabilize torso and place hands behind head.

2. Exhale as you pull navel in, curling torso upward. Imagine curling the bottom of rib cage and pelvis toward each other. Inhale as you lower to starting position. Do 15 reps.

Heel Tap

Steps:

1. Lie on back with heels on top of a stability ball, arms at sides, palms down.

2. Lift right heel slightly off ball and trace the curve of the ball with heel as you lower right foot and leg to floor, keeping abs tight and hips and back still. Lightly tap floor with heel then lift leg back to starting position. Repeat with other leg, do 10 taps per leg.