Trainer's Strategy
For a strong, sexy midriff, do exercises that use your core muscles (abdominals and spine extensors) to stabilize your torso as you move your legs.

Why it Works
This workout strengthens the midsection muscles that help you stand tall and lifted, says trainer Michelle McBryde. As you bend or scissor your legs, your abdominal and spine-extensor muscles work together to keep your trunk motionless. By maintaining equal tension in these opposing muscle groups, you can develop balanced strength that is key to beautiful posture, better coordination and a pain-free back. These exercises also stimulate deep, stabilizing muscles, including the transverse abdominis, to produce a flatter, firmer look, McBryde notes.

Muscle Mechanics
Your abdominal and spine-extensor muscles stabilize your torso. Your abs comprise the rectus abdominis, external and internal obliques, and transverse abdominis. The main back muscles involved are the erector spinae. They consist of three muscle pairs that run from your hips to your neck on either side of your spinal column, branching off to attach at your ribs and on your spine.

Details
Do these moves as part of a total-body strength-training program. You'll need a medium-resistance flex band, an exercise mat and a 55- or 65-centimeter physioball, all of which are available at gyms. Warm up by lying on your back and slowly rotating your knees from side to side, using your abs to maintain control. End with cat stretches: Get on all fours, then inhale as you arch your back; exhale as you round your spine. Repeat 3-4 times.

Shape Reader Model
Ginger Mitchell, 29, does 30 minutes of cardio 2-3 times a week, weight training for 20 minutes 2-3 times a week, and yoga or Pilates for 45 minutes twice a week. "Keep a fitness journal to mark your achievements," she says. "It'll help you stay motivated."

MUSCLES WORKED abdominals: 1. rectus abdominis 2. external obliques 3. internal obliques 4. transverse abdominis spine extensors: 5. erector spinae

What Works Rule No. 1 for a bikini worthy body: Learn how to connect with your core muscles, says Michelle McBryde, a certified trainer and Pilates instructor at Breakthru Fitness in Pasadena, Calif. "Until you know how to activate them, you won't get the full benefit from your workouts," says McBryde, a former dancer. McBryde recommends taking the extra time to understand the goal of each exercise and how to perform it effectively. Then remember to engage your core in all your other activities, from weight lifting to Spinning. It's a subtle difference that can generate significant results.

Double-leg Stretch Strengthens abdominals and spine extensors Lie on the floor with knees bent and in line with hips. Hold a resistance band around arches, heels together, elbows bent and on floor. Contract abs, keeping buttocks relaxed; this will help stabilize your torso. Draw your shoulder blades down; lift head and shoulders off the floor. Keeping abs tight, inhale as you extend legs out and hold at a 45-degree angle from the floor. Exhale as you lower head and return to starting position. Complete reps. TRAINER'S TIP Try to lengthen your spine (moving your head and tailbone away from each other) as you extend your legs.
Scissors Strengthens abdominals and spine extensors Lie on the floor with legs extended above hips, feet pointed toward the ceiling. Lift head, neck and shoulders off the floor and rest hands on calves. Squeeze shoulders down and back to stabilize upper body. Inhale, then exhale as you lower right leg to the mat about 6 inches from the floor. Continue to guide left leg toward chest with both hands. Inhale, then exhale as you switch legs. Continue to "scissor" legs, inhaling as you initiate the movement and exhaling as you move your legs. TRAINER'S TIP Keep your pelvis stable by keeping abs tight and flat as you scissor your legs; don't tilt it upward.
Ball Pike Strengthens abdominals and spine extensors Kneel behind a stability ball, then drape your body over the ball and slowly walk your hands forward into a plank position = arms straight and in line with shoulders knees or shins on top of ball, legs straight, feet together. Tighten core muscles to maintain position, keeping head and neck neutral. Contract abs, keeping legs straight, and flex at your hips to draw the ball under your torso, pulling with your legs and feet. Slowly return to starting position and repeat. TRAINER'S TIP As you roll the ball beneath you, concentrate on bringing your hips toward your ribs to avoid transferring weight to your shoulders.

Beginner/Intermediate Workout Schedule Do these exercises 2-3 times a week, taking a day off between workouts. Move quickly from one exercise to the next without resting in between. Progress to the advanced program after 4-6 weeks. exercise scissors double-leg stretch ball pike sets 1 1 1 reps 4-5 (Each leg equals 1 rep.) 8-10 8-10 weight range none none none

Advanced Workout Schedule To progress, add another set of reps and follow the variations noted. exercise scissors double-leg stretch ball pike sets 2 2 2 reps 8-10 (Each leg equals 1 rep.) 8-10 8-10 weight range none none none Special Instructions Place yourt hands behind your head while performing reps. Choke up on the flex band to increase resistance. Following each set, maintain last lifted pike position, then bend your knees and straighten legs 4-6 times before returning to end position.