Do 3 sets of each of the 4 moves, performing as many reps (1 second up, 1 second down) as possible until you feel a burning sensation in the muscles you’re working or you can no longer maintain proper form. Rest 15 seconds between sets. You’ll likely be able to do more reps during earlier sets and exercises — and that’s okay. After you can do 50 reps or hold a plank for 2 minutes for most sets, try the “Make it Harder” variations, change the order of the exercises, or do the moves after another type of workout.

1. Hipless Crunch (video)
This variation better targets abs by preventing hips and upper body from helping you lift.

Lie on back with legs lifted and bent, calves parallel to floor, and feet relaxed. Cross arms over chest with hands on shoulders. Contract abdominal muscles and lift head, shoulders, and upper back about 30 degrees off floor. Lower without touching head to floor. Exhale as you lift; inhale as you lower. *Prevention Fitness Lab testers averaged 25 reps per set.

Make It Easier:extend arms down at sides.

Make It Harder: Extend legs straight up.

Tips:

• Don’t pull chin toward chest.
• Focus on abs doing the work; imagine sliding rib cage toward hips.

Stop When…

• You start pulling or jerking up with head, neck, or shoulders.
• You can’t keep neck or shoulders relaxed.

2. No-Hands Reverse Crunch (video)
Instead of keeping arms at sides, where they can help abs, anchor them overhead to activate more belly muscles.

Lie faceup with arms overhead and hands grasping a heavy piece of furniture or railing. Raise feet into the air with legs bent. Contract abs, press back into floor, and lift hips off floor. Exhale as you lift; inhale as you lower. *Prevention Fitness Lab testers averaged 21 reps per set.

Make It Easier: Do the move with arms down at sides.

Make It Harder: Straighten legs.

Tips:

• Feel the contraction in abs, not in back or legs.
• Tilt pelvis.
• Think of lifting up instead of pulling knees toward chest.

Stop When…

• You can’t lift hips off the floor without jerking.
• Neck and shoulders are tense.

3. V Crunch (video)
This exercise gets your upper and lower body moving simultaneously to recruit the maximum number of muscle fibers in your midsection.

Balance on tailbone with legs bent, feet off floor, and arms bent at sides. Make sure back is straight and chest is lifted. Lean back and extend arms and legs, then pull back to start position. *Prevention Fitness Lab testers averaged 11 reps per set.

Make It Easier: Grasp sides of thighs with hands.

Make It Harder: Hold a 3- to 5-pound dumbbell in each hand.

Tips:

• Eyes gaze straight forward; keep chin parallel to floor.
• Don’t let back curve or shoulders rise toward ears.

Stop When…

• You can’t keep arms or legs up.
• You can’t keep chest lifted.
• Back or neck starts to hurt.

4. Side Plank (video)
Static balancing moves like this one are challenging because your deepest abs work really hard to hold your core in midair. Do them after crunches to ensure complete fatigue — and firm abs from every angle.

Lie on right side, elbow beneath shoulder, feet stacked, left hand on hip. Contract abs to lift hip and leg off floor. Hold until fatigued, noting your time. Do 3 sets before switching sides. *Prevention Fitness Lab testers averaged 19 seconds per side for each set.

Make It Easier: Bend legs and balance on bottom knee and side of lower leg.

Make It Harder: Straighten top arm toward sky.

Tips:

• Keep head, neck, torso, hips, and legs all in one straight line.
• Don’t sink into shoulder — press elbow into floor and lift torso.

Stop When…

• Hip is sagging toward floor.
• Neck, shoulder, or back hurts.
• You can’t keep body in line.

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