I am very excited to see how many people want to build a strong core, but many of these people go about it the wrong way. Old notions of endless crunches to get a flat stomach and visible ab muscles is not be the best approach. Pilates workouts are much better for developing a strong and aesthetic midsection because not only does it target the superficial abdominal muscles like crunches, but also recruits deep abdominal muscles to create strength all the way through the trunk of your body.
For those with back and hip problems who need to fix posture, performing large amounts of crunches can actually make the problem worse! The flexion created in the spine by the movement of crunching upward can further strengthen overdeveloped muscles while neglecting the weak muscles –exacerbating the imbalance.
If your goal is to reduce back and hip pain through improved posture and strength, regular practice of Pilates movements is your best bet.