Want a Strong Core? This Week-Long Ab Challenge From Tone It Up's Stef Corgel Is For You

Corgel said these work your deep core and rectus abdominis (six-pack muscles).

• Lie on the ground with your legs straight and arms by your ears, holding a dumbbell. You can modify this exercise by bending your knees. To modify even further, place a weight between your feet to anchor them down.
• Engage your core and begin to lift your shoulders and back off the ground, keeping your arms straight the entire time.
• Lift up to a sitting position — so your body makes an L shape — or as high as you can, keeping your arms by your ears and contracting your abdominal muscles throughout the movement.
• With control, slowly lower your body back down to the starting position, making sure your arms stay extended. This counts as one rep.