Like most women, I've always been determined to get a defined, flat stomach. But after years of doing 500 crunches during every workout, I learned that determination only gets you so far when the approach is wrong. Even an entire hour of crunches won't match the body benefits of a 10-minute plank workout.
The plank is one of the best exercises for a flat, toned stomach because it works all the muscles in your core, including the rectus abdominus (the "six-pack muscles" you can see), transverse abdominus, internal and external obliques, hips, and back.
Why not just focus on the six-pack muscles? Strengthening your entire core is not only crucial for sculpting a flat stomach, but these muscles also provide support for the entire body in everyday movements, reduce back pain, and improve posture. Plus, planks burn more calories than sit-ups or crunches because they recruit muscles in the legs, arms, and rear too. It's truly the ultimate total-body toner!
Here are some of my favorite plank variations. Start with the first four, holding each exercise for 30 seconds (work up to 1-minute holds). Do each plank variation once and then repeat the entire series 2 more times (3 times total). When you feel comfortable with the first four planks, advance to incorporate the next three (No. 5-7), holding each one for 30-60 seconds. For a killer core workout, combine all seven into one routine.
Related: Get more tips for a toned tummy with SHAPE's free iPad app. Access exclusive fat-blasting workouts, meal plans, and more!